CVE-2026-99281

Description

In the Linux kernel, the following vulnerability has been resolved: tun: Require CAP_NET_ADMIN to attach to an ownerless device Twenty years ago I made creating a tuntap device require CAP_NET_ADMIN in commit ca6bb5d7ab22 ("[NET]: Require CAP_NET_ADMIN to create tuntap devices.") The idea was to allow the permissions on /dev/net/tun to be relaxed to 0666 and thus allow owners of tun devices assigned with TUNSETOWNER to actually open it and get at their devices. What we missed at the time was that persistent devices with *no* owner were already essentially world-consumable, and anyone who could open the device node could also attach to those. Even then, using persistent devices with no explicitly set owner — on the (false) presumption that CAP_NET_ADMIN would be required to open them — wasn't an egregious userspace bug. There are cases where it does make sense to separate the creation/configuration of the netdevice, from the process which shovels packets into it. Since then, TUNSETGROUP was added a year later in commit 8c644623fe7e ("[NET]: Allow group ownership of TUN/TAP devices."). Its commit message noted that if both uid and gid are set, both have to match (in itself a bizarre choice) — but still not that with *neither* set, no permission at all was required. Then in 2012 commit c8d68e6be1c3 ("tuntap: multiqueue support") allowed new queues to be attached to a device from the moment of its creation, with no way for userspace to close the race between creation and a subsequent TUNSET{OWNER,GROUP}. In 2024, commit 3ca459eaba1bf ("tun: fix group permission check") tried to fix things to be saner: only require the user *or* the group to match, in line with standard POSIX permissions, and require CAP_NET_ADMIN if neither the user nor group authorised the access (although it put the CAP_NET_ADMIN check first, and would wrongly have reported the capability as having been used even when it was not). That fix was reverted in commit a70c7b3cbc06 ("tun: revert fix group permission check") due to allegedly causing a regression in an selinux test suite which *expected* the attachment to succeed when authorised by none of user, group, nor CAP_NET_ADMIN: https://lore.kernel.org/netdev/CAFqZXNtkCBT4f+PwyVRmQGoT3p1eVa01fCG_aNtpt6dakXncUg@mail.gmail.com/ We should not break UAPI. But we don't have to consider an selinux test case which deliberately exercises a security flaw to be UAPI worth preserving either. To which end, I have fixed it in selinux-testsuite commit b2f894f0016b ("tests/tun_tap: set an owner on the device for the relabel tests"). So: fix the lack of CAP_NET_ADMIN check on devices which *haven't* been assigned an owner or group, while leaving the weird tun ownership model as it was (user *and* group have to match, if both are set). If someone still wants to fix the latter (which wasn't actually the reason the previous attempt was reverted), they can do it under separate cover. Permit attaching to an existing device only if an owner and/or group was set and the caller matches all that were set, or if the caller has CAP_NET_ADMIN. The only behavioural change is that a device with no owner or group now requires CAP_NET_ADMIN to attach — precisely the loophole we want to close. And put the CAP_NET_ADMIN check in the right place this time.

Overview

State: PUBLISHED
Assigner (CNA): Linux
CVSS severity: —
CVSS score: —
CVSS vector: —
Effective score: no score available from CNA, NVD, or AI yet
CWE(s): —
Reserved: 2026-09-25
Published: 2026-11-07 14:08 UTC
Last updated: 2026-11-07 14:08 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/99xxx/CVE-2026-99281.json

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European Union Vulnerability Database ENISA EUVD

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EUVD ID: EUVD-2026-119281

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Affected products (2)

Vendor	Product	Versions	Platforms
Linux	Linux	`ca6bb5d7ab22ac79f608fe6cbc6b12de6a5a19f0` (affected), `ca6bb5d7ab22ac79f608fe6cbc6b12de6a5a19f0` (affected), `ca6bb5d7ab22ac79f608fe6cbc6b12de6a5a19f0` (affected)	—
Linux	Linux	`2.6.18` (affected), `0` (unaffected), `6.18.61` (unaffected), `7.3.2` (unaffected), `7.4-rc1` (unaffected)	—

Vendor references (3)

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

Web references (0)

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

No web references attached yet.

Remediations (10)

CVE-2026-99281 - Red Hat Customer Portal

web:access.redhat.com

Overall, you have the following options: Upgrade to a supported product version that includes a fix for this vulnerability (recommended). Apply a mitigation (if one exists). Customers with the Technical Account Manager (TAM) RHEL Security Select Add-on can review this CVE directly with their TAM.

2026-11-08 11:05 UTC
Security Updates - Red Hat Customer Portal

web:access.redhat.com

Products & tools Red Hat Documentation Find answers, get guidance, and learn how to use Red Hat products. Red Hat Ecosystem Catalog Find hardware, software, and cloud providers―and download container images―certified to perform with Red Hat technologies.

2026-11-08 11:05 UTC
October 2026 Critical Patch Update Released | security

web:blogs.oracle.com

For more information about the Critical Patch Update program, see the security vulnerability remediation practices page located on the Oracle Trust Center.

2026-11-08 11:05 UTC
CVE Database Search & Remediation Guidance

web:cvedatabase.com

Search and analyze CVE vulnerabilities with instant access to CVSS scores, affected products, and remediation guidance.

2026-11-08 11:05 UTC
CVE-2026-99281: Linux Vulnerability - CVETodo

web:cvetodo.com

CVE-2026-99281 vulnerability details and analysis. Full technical analysis, mitigations , and exploit status — updated in real time.

2026-11-08 11:05 UTC
SAP Security Patch Day - October 2026

web:support.sap.com

On 13 th of October 2026 , SAP security patch day saw the release of 16 new security notes and 4 GitHub security advisories. There are 2 updates to previously released security notes.

2026-11-08 11:05 UTC
CVE-2026-99281 - vulnerability database | Vulners.com

web:vulners.com

CVE-2026-99281 🗓️ 07 Nov 2026 06:08:47 Reported by Linux Type cve 🔗 web.nvd.nist.gov 👁 15 Views

2026-11-08 11:05 UTC
Critical Patch Updates, Critical Security Patch Updates ... - Oracle

web:www.oracle.com

Critical Security Patch Updates Critical Security Patch Updates provide security patches for supported Oracle on-premises products. A Critical Security Patch Update provides targeted, high-priority security fixes in a smaller, more focused format, making them easier to apply with minimal disruption.

2026-11-08 11:05 UTC
Oracle Critical Patch Update Advisory - July 2026

web:www.oracle.com

This Critical Patch Update contains 1448 new security patches across the product families listed below. Please note that a My Oracle Support (MOS) note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at July 2026 Critical Patch Update: Executive Summary and Analysis.

2026-11-08 11:05 UTC
CVE-2026-99281: 2024 Security Vulnerability - Analysis & Fix ...

web:www.thehackerwire.com

How do I fix or mitigate CVE-2026-99281 ? To protect against CVE-2026-99281 , you should: (1) Apply the latest security patches from the vendor, (2) Check official security advisories for specific remediation steps, (3) Update affected software to the latest version, and (4) Monitor your systems for any signs of exploitation.

2026-11-08 11:05 UTC

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-99281.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/tun.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "2f92c0286cfd58bff9d6d54c01a771073d5eb775",
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              "versionType": "git"
            },
            {
              "lessThan": "e53d1cf05da8ea58a5743b7ce5894fb51b0b9700",
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            {
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              "versionType": "git"
            }
          ]
        },
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          "defaultStatus": "affected",
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          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.18"
            },
            {
              "lessThan": "2.6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.61",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.3.*",
              "status": "unaffected",
              "version": "7.3.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.4-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.61",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3.2",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.4-rc1",
                  "versionStartIncluding": "2.6.18",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntun: Require CAP_NET_ADMIN to attach to an ownerless device\n\nTwenty years ago I made creating a tuntap device require CAP_NET_ADMIN\nin commit ca6bb5d7ab22 (\"[NET]: Require CAP_NET_ADMIN to create tuntap\ndevices.\")\n\nThe idea was to allow the permissions on /dev/net/tun to be relaxed to\n0666 and thus allow owners of tun devices assigned with TUNSETOWNER to\nactually open it and get at their devices.\n\nWhat we missed at the time was that persistent devices with *no* owner\nwere already essentially world-consumable, and anyone who could open\nthe device node could also attach to those.\n\nEven then, using persistent devices with no explicitly set owner \u2014 on\nthe (false) presumption that CAP_NET_ADMIN would be required to open\nthem \u2014 wasn't an egregious userspace bug. There are cases where it does\nmake sense to separate the creation/configuration of the netdevice, from\nthe process which shovels packets into it.\n\nSince then, TUNSETGROUP was added a year later in commit 8c644623fe7e\n(\"[NET]: Allow group ownership of TUN/TAP devices.\"). Its commit message\nnoted that if both uid and gid are set, both have to match (in itself a\nbizarre choice) \u2014 but still not that with *neither* set, no permission\nat all was required.\n\nThen in 2012 commit c8d68e6be1c3 (\"tuntap: multiqueue support\") allowed\nnew queues to be attached to a device from the moment of its creation,\nwith no way for userspace to close the race between creation and a\nsubsequent TUNSET{OWNER,GROUP}.\n\nIn 2024, commit 3ca459eaba1bf (\"tun: fix group permission check\") tried\nto fix things to be saner: only require the user *or* the group to\nmatch, in line with standard POSIX permissions, and require\nCAP_NET_ADMIN if neither the user nor group authorised the access\n(although it put the CAP_NET_ADMIN check first, and would wrongly have\nreported the capability as having been used even when it was not).\n\nThat fix was reverted in commit a70c7b3cbc06 (\"tun: revert fix group\npermission check\") due to allegedly causing a regression in an selinux\ntest suite which *expected* the attachment to succeed when authorised\nby none of user, group, nor CAP_NET_ADMIN:\nhttps://lore.kernel.org/netdev/CAFqZXNtkCBT4f+PwyVRmQGoT3p1eVa01fCG_aNtpt6dakXncUg@mail.gmail.com/\n\nWe should not break UAPI. But we don't have to consider an selinux test\ncase which deliberately exercises a security flaw to be UAPI worth\npreserving either. To which end, I have fixed it in selinux-testsuite\ncommit b2f894f0016b (\"tests/tun_tap: set an owner on the device for the\nrelabel tests\").\n\nSo: fix the lack of CAP_NET_ADMIN check on devices which *haven't* been\nassigned an owner or group, while leaving the weird tun ownership model\nas it was (user *and* group have to match, if both are set). If someone\nstill wants to fix the latter (which wasn't actually the reason the\nprevious attempt was reverted), they can do it under separate cover.\n\nPermit attaching to an existing device only if an owner and/or group was\nset and the caller matches all that were set, or if the caller has\nCAP_NET_ADMIN. The only behavioural change is that a device with no\nowner or group now requires CAP_NET_ADMIN to attach \u2014 precisely the\nloophole we want to close.\n\nAnd put the CAP_NET_ADMIN check in the right place this time."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-07T14:08:47.735Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2f92c0286cfd58bff9d6d54c01a771073d5eb775"
        },
        {
          "url": "https://git.kernel.org/stable/c/e53d1cf05da8ea58a5743b7ce5894fb51b0b9700"
        },
        {
          "url": "https://git.kernel.org/stable/c/ffdf678dd16610e3f006dac904bd37c09684673c"
        }
      ],
      "title": "tun: Require CAP_NET_ADMIN to attach to an ownerless device",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99281",
    "datePublished": "2026-11-07T14:08:47.735Z",
    "dateReserved": "2026-09-25T10:25:14.405Z",
    "dateUpdated": "2026-11-07T14:08:47.735Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}