CVE-2026-23074

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: Enforce that teql can only be used as root qdisc Design intent of teql is that it is only supposed to be used as root qdisc. We need to check for that constraint. Although not important, I will describe the scenario that unearthed this issue for the curious. GangMin Kim <km.kim1503@gmail.com> managed to concot a scenario as follows: ROOT qdisc 1:0 (QFQ) ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s └── class 1:2 (weight=1, lmax=1514) teql GangMin sends a packet which is enqueued to 1:1 (netem). Any invocation of dequeue by QFQ from this class will not return a packet until after 6.4s. In the meantime, a second packet is sent and it lands on 1:2. teql's enqueue will return success and this will activate class 1:2. Main issue is that teql only updates the parent visible qlen (sch->q.qlen) at dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's peek always returns NULL), dequeue will never be called and thus the qlen will remain as 0. With that in mind, when GangMin updates 1:2's lmax value, the qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's qlen was not incremented, qfq fails to deactivate the class, but still frees its pointers from the aggregate. So when the first packet is rescheduled after 6.4 seconds (netem's delay), a dangling pointer is accessed causing GangMin's causing a UAF.

Overview

State: PUBLISHED
Assigner (CNA): Linux
CVSS severity: HIGH
CVSS score: 7.8 / 10
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Effective score: 7.8 / 10 HIGH source: CNA overview
CWE(s): —
Reserved: 2026-01-13
Published: 2026-02-04 17:07 UTC
Last updated: 2026-05-11 23:59 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/23xxx/CVE-2026-23074.json
Linked Threat: CVE-2026-23074 — net/sched: Enforce that teql can only be used as root qdisc

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-02-04 17:16:18 UTC
NVD last modified: 2026-04-03 14:16:22 UTC
NVD CVSS v3.1: 7.8 / 10 HIGH source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Exploitability subscore: 1.8 / 10
Impact subscore: 5.9 / 10
EPSS score: 0.0002 (probability of exploitation in next 30 days)
EPSS percentile: 4.31% vs all CVEs — higher = more likely to be exploited, as of 2026-05-25

NVD-assigned CWE(s): CWE-416 (differs from the CNA list above)

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-5470
Assigner: Linux
Published: Feb 4, 2026, 4:07:59 PM
Updated: May 11, 2026, 9:59:29 PM
EUVD base score (CVSS 3.1): 7.8 / 10
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EUVD-reported EPSS: 0.0200
Vendors: Linux
Products: Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <16ed73c1282d376b956bff23e5139add061767ba)

Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <4c7e8aa71c9232cba84c289b4b56cba80b280841)

Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <73d970ff0eddd874a84c953387c7f4464b705fc6)

Linux (patch: 5.10.249)

Linux (patch: 5.15.199)

Linux (2.6.12)

Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ae810e6a8ac4fe25042e6825d2a401207a2e41fb)

Linux (patch: 0)

Linux (patch: 6.18.8)

Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <dad49a67c2d817bfec98e6e45121b351e3a0202c)

Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0686bedfed34155520f3f735cbf3210cb9044380)

Linux (patch: 6.19-rc7)

Linux (patch: 6.1.162)

Linux (patch: 6.6.122)

Linux (patch: 6.19)

Linux (patch: 6.12.68)

Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b)
Aliases: GHSA-7cwq-2xv8-7cqw

ENISA description: In the Linux kernel, the following vulnerability has been resolved: net/sched: Enforce that teql can only be used as root qdisc Design intent of teql is that it is only supposed to be used as root qdisc. We need to check for that constraint. Although not important, I will describe the scenario that unearthed this issue for the curious. GangMin Kim <km.kim1503@gmail.com> managed to concot a scenario as follows: ROOT qdisc 1:0 (QFQ) ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s └── class 1:2 (weight=1, lmax=1514) teql GangMin sends a packet which is enqueued to 1:1 (netem). Any invocation of dequeue by QFQ from this class will not return a packet until after 6.4s. In the meantime, a second packet is sent and it lands on 1:2. teql's enqueue will return success and this will activate class 1:2. Main issue is that teql only updates the parent visible qlen (sch->q.qlen) at dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's peek always returns NULL), dequeue will never be called and thus the qlen will remain as 0. With that in mind, when GangMin updates 1:2's lmax value, the qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's qlen was not incremented, qfq fails to deactivate the class, but still frees its pointers from the aggregate. So when the first packet is rescheduled after 6.4 seconds (netem's delay), a dangling pointer is accessed causing GangMin's causing a UAF.

EUVD references (7)

Affected products (2)

Vendor	Product	Versions	Platforms
Linux	Linux	`1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected)	—
Linux	Linux	`2.6.12` (affected), `0` (unaffected), `5.10.249` (unaffected), `5.15.199` (unaffected), `6.1.162` (unaffected), `6.6.122` (unaffected), `6.12.68` (unaffected), `6.18.8` (unaffected), `6.19` (unaffected)	—

Affected products — CPE 2.3 (12) NVD

NVD's normalized CPE 2.3 matchers, used by vendor tools (vulnerability scanners, asset managers) for automated detection. Compare with the CNA's free-text "Affected products" section above.

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:2.6.12:-:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:2.6.12:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:2.6.12:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:2.6.12:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:2.6.12:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.19:rc6:*:*:*:*:*:*

Vendor references (7)

References embedded in the original CVE record by the assigning CNA.

MITRE references (7) cveawg.mitre.org

Pulled from MITRE's CVE Services API by the 🛰 Backfill from MITRE button.

Web references (8)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

https://alas.aws.amazon.com/AL2023/ALAS-2026-1455.html rapid7:alas.aws.amazon.com
https://alas.aws.amazon.com/AL2023/ALAS-2026-1468.html rapid7:alas.aws.amazon.com
https://www.cve.org/CVERecord?id=CVE-2026-23074 rapid7:www.cve.org
https://attackerkb.com/topics/CVE-2026-23074 rapid7:attackerkb.com
https://errata.almalinux.org/8/ALSA-2026-3083.html rapid7:errata.almalinux.org
https://errata.almalinux.org/8/ALSA-2026-3110.html rapid7:errata.almalinux.org
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-5470 rapid7:euvd.enisa.europa.eu
http://cwe.mitre.org/data/definitions/416.html rapid7:cwe.mitre.org

NVD-tagged references (7)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://git.kernel.org/stable/c/0686bedfed34155520f3f735cbf3210cb9044380 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Patch
https://git.kernel.org/stable/c/16ed73c1282d376b956bff23e5139add061767ba 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Patch
https://git.kernel.org/stable/c/4c7e8aa71c9232cba84c289b4b56cba80b280841 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Patch
https://git.kernel.org/stable/c/50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Patch
https://git.kernel.org/stable/c/73d970ff0eddd874a84c953387c7f4464b705fc6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Patch
https://git.kernel.org/stable/c/ae810e6a8ac4fe25042e6825d2a401207a2e41fb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Patch
https://git.kernel.org/stable/c/dad49a67c2d817bfec98e6e45121b351e3a0202c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Patch

Indicators (3)

IOCs linked to the auto-promoted Threat row.

Type	Value	VirusTotal	Attached
domain	`gmail.com`	2026-05-22 02:46 UTC)">not flagged UrlVoid 0 / 35	2026-05-18 21:18 UTC
domain	`q.qlen`	no local data	2026-05-18 21:18 UTC
ipv4	`142.250.188.165`	no local data	2026-08-04 22:15 UTC

Remediations (12)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

Known Exploited Vulnerabilities Catalog - CISA

web:www.cisa.gov

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild. Organizations should use the KEV catalog as an input to their vulnerability management prioritization framework.

2026-05-22 15:56 UTC
Trend Micro warns of Apex One zero-day exploited in the wild

web:www.bleepingcomputer.com

Japanese cybersecurity software company Trend Micro has addressed an Apex One zero-day vulnerability exploited in attacks targeting Windows systems.

2026-05-22 15:56 UTC
Microsoft Patch Tuesday May 2026 - 120 Vulnerabilities Fixed, Including ...

web:cybersecuritynews.com

Microsoft's May 2026 Patch Tuesday lands with a heavy enterprise focus, fixing 120 vulnerabilities across Windows, Office, Azure, developer tools, and Microsoft 365 apps, including 29 remote code execution (RCE) flaws rated Critical.

2026-05-22 03:24 UTC
Nvd - Cve-2026-26074

web:nvd.nist.gov

An official website of the United States government Here's how you know

2026-05-22 03:24 UTC
Security Update Guide - Loading - Microsoft

web:portal.msrc.microsoft.com

The Security Update Guide provides information on the latest Microsoft security updates, helping users understand and address potential vulnerabilities effectively.

2026-05-22 03:24 UTC
2 New Microsoft Defender Zero-Days Exploited—Patch Now ... - Forbes

web:www.forbes.com

Microsoft has confirmed an emergency security update as CISA warns that two new Defender zero-days are being exploited by attackers.

2026-05-22 03:24 UTC
Oracle Critical Patch Update Advisory - April 2026

web:www.oracle.com

This Critical Patch Update contains 481 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at April 2026 Critical Patch Update: Executive Summary and Analysis.

2026-05-22 03:24 UTC
VirusTotal - Home

web:www.virustotal.com

VirusTotal is a platform for scanning files and URLs for viruses, malware, and other threats using multiple antivirus engines.

2026-05-22 03:24 UTC
Windows 11 April 2026 Update tested: What's new, improved and fixed

web:www.windowslatest.com

Windows 11 April 2026 update adds Narrator Copilot support, faster Settings, File Explorer fixes, and key security improvements.

2026-05-22 03:24 UTC
cve-details - Red Hat Customer Portal

web:access.redhat.com

Learn about our open source products, services, and company. You are here

2026-05-22 03:24 UTC
Patch Tuesday May 2026: Security Updates & CVE Analysis

web:zecurit.com

Get the complete breakdown of Microsoft's May 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .

2026-05-22 03:24 UTC
Microsoft and Adobe Patch Tuesday, May 2026 Security Update Review

web:blog.qualys.com

May 2026's Patch Tuesday arrives with Microsoft addressing a fresh set of vulnerabilities across its ecosystem, reinforcing the ongoing need for timely patching in an increasingly threat-heavy…

2026-05-22 03:24 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-23074.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/sch_teql.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "73d970ff0eddd874a84c953387c7f4464b705fc6",
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              "versionType": "git"
            },
            {
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              "status": "affected",
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              "versionType": "git"
            },
            {
              "lessThan": "dad49a67c2d817bfec98e6e45121b351e3a0202c",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "0686bedfed34155520f3f735cbf3210cb9044380",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "4c7e8aa71c9232cba84c289b4b56cba80b280841",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "16ed73c1282d376b956bff23e5139add061767ba",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "lessThan": "2.6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.249",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.199",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.162",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.122",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.68",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.249",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.199",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.1.162",
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                  "vulnerable": true
                },
                {
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.68",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.8",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: Enforce that teql can only be used as root qdisc\n\nDesign intent of teql is that it is only supposed to be used as root qdisc.\nWe need to check for that constraint.\n\nAlthough not important, I will describe the scenario that unearthed this\nissue for the curious.\n\nGangMin Kim <km.kim1503@gmail.com> managed to concot a scenario as follows:\n\nROOT qdisc 1:0 (QFQ)\n  \u251c\u2500\u2500 class 1:1 (weight=15, lmax=16384) netem with delay 6.4s\n  \u2514\u2500\u2500 class 1:2 (weight=1, lmax=1514) teql\n\nGangMin sends a packet which is enqueued to 1:1 (netem).\nAny invocation of dequeue by QFQ from this class will not return a packet\nuntil after 6.4s. In the meantime, a second packet is sent and it lands on\n1:2. teql's enqueue will return success and this will activate class 1:2.\nMain issue is that teql only updates the parent visible qlen (sch->q.qlen)\nat dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's\npeek always returns NULL), dequeue will never be called and thus the qlen\nwill remain as 0. With that in mind, when GangMin updates 1:2's lmax value,\nthe qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's\nqlen was not incremented, qfq fails to deactivate the class, but still\nfrees its pointers from the aggregate. So when the first packet is\nrescheduled after 6.4 seconds (netem's delay), a dangling pointer is\naccessed causing GangMin's causing a UAF."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T21:59:29.932Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/73d970ff0eddd874a84c953387c7f4464b705fc6"
        },
        {
          "url": "https://git.kernel.org/stable/c/ae810e6a8ac4fe25042e6825d2a401207a2e41fb"
        },
        {
          "url": "https://git.kernel.org/stable/c/dad49a67c2d817bfec98e6e45121b351e3a0202c"
        },
        {
          "url": "https://git.kernel.org/stable/c/0686bedfed34155520f3f735cbf3210cb9044380"
        },
        {
          "url": "https://git.kernel.org/stable/c/4c7e8aa71c9232cba84c289b4b56cba80b280841"
        },
        {
          "url": "https://git.kernel.org/stable/c/16ed73c1282d376b956bff23e5139add061767ba"
        },
        {
          "url": "https://git.kernel.org/stable/c/50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b"
        }
      ],
      "title": "net/sched: Enforce that teql can only be used as root qdisc",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-23074",
    "datePublished": "2026-02-04T16:07:59.379Z",
    "dateReserved": "2026-01-13T15:37:45.958Z",
    "dateUpdated": "2026-05-11T21:59:29.932Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}