CVE-2026-43503

CVEs › CVE-2026-43503

Description

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: propagate shared-frag marker through frag-transfer helpers Two frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()->flags when moving frags from source to destination. __pskb_copy_fclone() defers the rest of the shinfo metadata to skb_copy_header() after copying frag descriptors, but that helper only carries over gso_{size,segs, type} and never touches skb_shinfo()->flags; skb_shift() moves frag descriptors directly and leaves flags untouched. As a result, the destination skb keeps a reference to the same externally-owned or page-cache-backed pages while reporting skb_has_shared_frag() as false. The mismatch is harmful in any in-place writer that uses skb_has_shared_frag() to decide whether shared pages must be detoured through skb_cow_data(). ESP input is one such writer (esp4.c, esp6.c), and a single nft 'dup to <local>' rule -- or any other nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d skb in esp_input() with the marker stripped, letting an unprivileged user write into the page cache of a root-owned read-only file via authencesn-ESN stray writes. Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors were actually moved from the source. skb_copy() and skb_copy_expand() share skb_copy_header() too but linearize all paged data into freshly allocated head storage and emerge with nr_frags == 0, so skb_has_shared_frag() returns false on its own; they need no change. The same omission exists in skb_gro_receive() and skb_gro_receive_list(). The former moves the incoming skb's frag descriptors into the accumulator's last sub-skb via two paths (a direct frag-move loop and the head_frag + memcpy path); the latter chains the incoming skb whole onto p's frag_list. Downstream skb_segment() reads only skb_shinfo(p)->flags, and skb_segment_list() reuses each sub-skb's shinfo as the nskb -- both p and lp must carry the marker. The same omission also exists in tcp_clone_payload(), which builds an MTU probe skb by moving frag descriptors from skbs on sk_write_queue into a freshly allocated nskb. The helper falls into the same family and warrants the same fix for consistency; no TCP TX-side in-place writer is currently known to reach a user page through this gap, but a future consumer depending on the marker would regress silently. The same omission exists in skb_segment(): the per-iteration flag merge takes only head_skb's flag, and the inner switch that rebinds frag_skb to list_skb on head_skb-frags exhaustion does not fold the new frag_skb's flag into nskb. Fold frag_skb's flag at both sites so segments drawing frags from frag_list members carry the marker.

Overview

State: PUBLISHED
Assigner (CNA): Linux
CVSS severity: high
CVSS score: 8.8 / 10
CVSS vector: AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Effective score: 8.8 / 10 HIGH source: CNA overview
MSRC score: 7.0 / 10 HIGH MS rating: Important
CWE(s): —
Reserved: 2026-05-01
Published: 2026-05-23 11:44 UTC
Last updated: 2026-05-23 13:20 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/43xxx/CVE-2026-43503.json
Linked Threat: CVE-2026-43503 — CVE-2026-43503

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.

EPSS score: 0.0002 (probability of exploitation in next 30 days)
EPSS percentile: 7.23% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

NVD / KEV / EPSS data refreshed 2026-05-25 00:20 UTC. Re-run the 🛰 Backfill from NVD button above to refresh.

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-2026-31536
Assigner: Linux
Published: May 23, 2026, 11:44:01 AM
Updated: May 30, 2026, 10:45:26 AM
EUVD base score (CVSS 3.1): 8.8 / 10
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
EUVD-reported EPSS: 0.0100
Vendors: Linux
Products: Linux (patch: 6.12.91)

Linux (patch: 5.15.208)

Linux (patch: 6.1.174)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <3bd9e113d50034db99d7ef69fd8e5242d15e414a)

Linux (patch: 6.6.141)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <3884358a9286b17f389a72b1426fc4547c23c111)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <48f6a5356a33dd78e7144ae1faef95ffc990aae0)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <ff375cc75f9167168db38e0464a482d5fbc8d81d)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <9bc9d6d6967a2239aa57af2aa53554eddd640d20)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <9d3e5fd19fe1063bf607219e8562fbd567b8e8d5)

Linux (patch: 0)

Linux (patch: 7.1-rc5)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <12401fcfb01f53ccc63ab0a3246570fe8f3105ee)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <3599e6b3cc1ada96883d496a50a210d3afbb6987)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8)

Linux (patch: 7.0.10)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <2f2b16022a2e10ca7bccfb98db5ed2ec0f72641c)

Linux (patch: 6.18.33)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <fbeab9555564a1b98e8582cd106dfe46c4606991)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <989214c66884d70716d83dc1d0bf5e16287bf349)

Linux (3.9)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <179f1852bdedc300e373e807cc102cd81feff196)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <760e1addc27ba1a7beb4a0a7e8b3e9ec49e7a34e)

Linux (patch: 5.10.257)

Linux (cef401de7be8c4e155c6746bfccf721a4fa5fab9 <78bf6b6bb19541d19fbda6242e7cfe2c682763c0)
Aliases: GHSA-494p-q444-9xf7

ENISA description: In the Linux kernel, the following vulnerability has been resolved: net: skbuff: propagate shared-frag marker through frag-transfer helpers Two frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()->flags when moving frags from source to destination. __pskb_copy_fclone() defers the rest of the shinfo metadata to skb_copy_header() after copying frag descriptors, but that helper only carries over gso_{size,segs, type} and never touches skb_shinfo()->flags; skb_shift() moves frag descriptors directly and leaves flags untouched. As a result, the destination skb keeps a reference to the same externally-owned or page-cache-backed pages while reporting skb_has_shared_frag() as false. The mismatch is harmful in any in-place writer that uses skb_has_shared_frag() to decide whether shared pages must be detoured through skb_cow_data(). ESP input is one such writer (esp4.c, esp6.c), and a single nft 'dup to <local>' rule -- or any other nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d skb in esp_input() with the marker stripped, letting an unprivileged user write into the page cache of a root-owned read-only file via authencesn-ESN stray writes. Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors were actually moved from the source. skb_copy() and skb_copy_expand() share skb_copy_header() too but linearize all paged data into freshly allocated head storage and emerge with nr_frags == 0, so skb_has_shared_frag() returns false on its own; they need no change. The same omission exists in skb_gro_receive() and skb_gro_receive_list(). The former moves the incoming skb's frag descriptors into the accumulator's last sub-skb via two paths (a direct frag-move loop and the head_frag + memcpy path); the latter chains the incoming skb whole onto p's frag_list. Downstream skb_segment() reads only skb_shinfo(p)->flags, and skb_segment_list() reuses each sub-skb's shinfo as the nskb -- both p and lp must carry the marker. The same omission also exists in tcp_clone_payload(), which builds an MTU probe skb by moving frag descriptors from skbs on sk_write_queue into a freshly allocated nskb. The helper falls into the same family and warrants the same fix for consistency; no TCP TX-side in-place writer is currently known to reach a user page through this gap, but a future consumer depending on the marker would regress silently. The same omission exists in skb_segment(): the per-iteration flag merge takes only head_skb's flag, and the inner switch that rebinds frag_skb to list_skb on head_skb-frags exhaustion does not fold the new frag_skb's flag into nskb. Fold frag_skb's flag at both sites so segments drawing frags from frag_list members carry the marker.

EUVD references (8)

Microsoft Security Response Center MSRC

Microsoft's vendor-authoritative record from the Security Update Guide — its own CVSS score, impact, severity rating, exploit assessment, and KB-article fixes. Refreshed 2026-08-12 01:09 UTC (source: CVRF).

MS severity: Important
MS CVSS base score: 7.0 / 10 (temporal 7.0)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Release: 2026-May

Microsoft remediations / KB articles (2)

CBL-Mariner Releases — Vendor Fix / Security Update (fixed build 6.6.141.1-1)
https://learn.microsoft.com/en-us/azure/azure-linux/tutorial-azure-linux-upgrade — None Available / CBL-Mariner Releases

Affected products (2)

Vendor	Product	Versions	Platforms
Linux	Linux	`cef401de7be8c4e155c6746bfccf721a4fa5fab9` (affected), `cef401de7be8c4e155c6746bfccf721a4fa5fab9` (affected), `cef401de7be8c4e155c6746bfccf721a4fa5fab9` (affected), `cef401de7be8c4e155c6746bfccf721a4fa5fab9` (affected), `cef401de7be8c4e155c6746bfccf721a4fa5fab9` (affected), `cef401de7be8c4e155c6746bfccf721a4fa5fab9` (affected), `cef401de7be8c4e155c6746bfccf721a4fa5fab9` (affected)	—
Linux	Linux	`3.9` (affected), `0` (unaffected), `5.10.257` (unaffected), `5.15.208` (unaffected), `6.1.174` (unaffected), `6.6.141` (unaffected), `6.12.91` (unaffected), `6.18.33` (unaffected), `7.0.10` (unaffected)	—

Vendor references (7)

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

Web references (13)

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

MSRC update guide: CVE-2026-43503 msrc
None Available msrc
https://git.kernel.org/stable/c/48f6a5356a33dd78e7144ae1faef95ffc990aae0 tenable:git.kernel.org
https://git.kernel.org/stable/c/989214c66884d70716d83dc1d0bf5e16287bf349 tenable:git.kernel.org
https://git.kernel.org/stable/c/9bc9d6d6967a2239aa57af2aa53554eddd640d20 tenable:git.kernel.org
https://git.kernel.org/stable/c/fbeab9555564a1b98e8582cd106dfe46c4606991 tenable:git.kernel.org
https://git.kernel.org/stable/c/fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8 tenable:git.kernel.org
https://git.kernel.org/stable/c/ff375cc75f9167168db38e0464a482d5fbc8d81d tenable:git.kernel.org
https://nvd.nist.gov/vuln/detail/CVE-2026-43503 tenable:nvd.nist.gov
https://www.cve.org/CVERecord?id=CVE-2026-43503 tenable:www.cve.org
https://git.kernel.org/stable/c/12401fcfb01f53ccc63ab0a3246570fe8f3105ee tenable:git.kernel.org
https://www.first.org/epss/ tenable:www.first.org
https://git.kernel.org/stable/c/179f1852bdedc300e373e807cc102cd81feff196 tenable:git.kernel.org

Remediations (17)

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

RHSB-2026-003 Networking subsystem Privilege Escalation - Linux Kernel ...

web:access.redhat.com

The mitigation methods below address both vulnerabilities that affect Red Hat products — CVE - 2026 -43284 (IPsec ESP) and CVE - 2026 -46300 (XFRM ESP-in-TCP). CVE - 2026 -43500 (rxrpc) does not affect Red Hat products and requires no mitigation .

2026-05-26 03:10 UTC
Security Advisory Bulletin 064 | Ubiquiti Community

web:community.ui.com

Published: May 21, 2026 Updated: May 22, 2026 Version: 1.1 Revision: 1.1 Summary 1 of 5 A malicious actor with access to the network and high privileges could exploit an Improper Input Validation vulnerability found in UniFi OS devices to execute a Command Injection. Affected Products: UniFi OS Server (Version 5.0.6 and earlier) Mitigation : Update your UniFi OS Server to Version 5.0.8 or later ...

2026-05-26 03:10 UTC
Microsoft Patch Tuesday March 2026 - 78 Vulnerabilities Fixed ...

web:cybersecuritynews.com

Microsoft released its March 2026 Patch Tuesday security update on March 10, 2026 , addressing 78 vulnerabilities across Windows, Microsoft Office, Azure, SQL Server, and .NET. The update includes one actively exploited zero-day vulnerability and multiple Critical-rated flaws demanding immediate attention from security teams. The most urgent fix this month is CVE - 2026 -21262, the sole zero-day ...

2026-05-26 03:10 UTC
Security Update Guide - Microsoft Security Response Center

web:msrc.microsoft.com

Security Update Guide - Microsoft Security Response Center

2026-05-26 03:10 UTC
Nvd - Cve-2026-43512

web:nvd.nist.gov

Official websites use .gov A .gov website belongs to an official government organization in the United States.

2026-05-26 03:10 UTC
Microsoft April 2026 Patch Tuesday fixes 167 flaws, 2 zero-days

web:www.bleepingcomputer.com

Today is Microsoft's April 2026 Patch Tuesday with security updates for 167 flaws, including 2 zero-day vulnerabilities.

2026-05-26 03:10 UTC
"DirtyFrag" (CVE-2026-43500, CVE-2026-43284) Mitigations - Linode

web:www.linode.com

The " DirtyFrag " ( CVE - 2026 -43500, CVE - 2026 -43284) vulnerabilities are the second in a new series of local privilege escalations in the Linux kernel that have recently been published and which exploit the ability for an unprivileged user to write to the page cache. Similar to the " CopyFail " ( CVE - 2026 -31431) vulnerability in nature, these new attack vectors exploit the esp4/esp6 (used ...

2026-05-26 03:10 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.

2026-05-26 03:10 UTC
Vulnerability Remediation vs. Mitigation: What are the Differences ...

web:www.secure.com

Learn the difference between vulnerability remediation and mitigation , and how a risk-based strategy can strengthen your security posture.

2026-05-26 03:10 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 .

2026-05-26 03:10 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.

2026-06-19 02:25 UTC
Security Update Guide - Microsoft Security Response Center

web:msrc.microsoft.com

Access Microsoft Security Response Center's guide to address vulnerabilities, manage security risks, and keep your systems protected with the latest updates.

2026-06-19 02:25 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.

2026-06-19 02:25 UTC
Three CVEs and the May 2026 Exploit Chain Nobody's Taking Seriously

web:securityboulevard.com

CISA added it to the Known Exploited Vulnerabilities catalog with a May 15 remediation deadline. Then there's CVE - 2026 -43284 and CVE - 2026 -43500, "Dirty Frag," disclosed May 7 by Hyunwoo Kim. It's a two-bug chain that lands in the same place as Copy Fail - page-cache-to-root LPE - but routes around the Copy Fail mitigation entirely.

2026-06-19 02:25 UTC
SAP Security Patch Day - February 2026

web:support.sap.com

SAP security Patch Day Bulletin This post shares the information on security notes that remediate vulnerabilities discovered in SAP products. SAP strongly recommends that the customer visits the Support Portal and applies patches on priority to protect their SAP landscape. On 10th of February 2026 , SAP security patch day saw the release of 26 new security notes. Further, there was 1 update to ...

2026-06-19 02:25 UTC
Oracle Critical Security Patch Update Advisory - May 2026

web:www.oracle.com

This Critical Security Patch Update contains 35 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Security Patch Update and other Oracle Software Security Assurance activities is located at May 2026 Critical Security Patch Update: Executive Summary and Analysis.

2026-06-19 02:25 UTC
Dirty Frag LPE: CVE-2026-43284 and CVE-2026-43500 Deep Dive

web:www.picussecurity.com

Dirty Frag chains CVE - 2026 -43284 and CVE - 2026 -43500 for Linux root privilege escalation. Learn how it works, how to remediate, and how to simulate it.

2026-06-19 02:25 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-43503.json.

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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: skbuff: propagate shared-frag marker through frag-transfer helpers\n\nTwo frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail\nto propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()->flags when\nmoving frags from source to destination.  __pskb_copy_fclone() defers\nthe rest of the shinfo metadata to skb_copy_header() after copying\nfrag descriptors, but that helper only carries over gso_{size,segs,\ntype} and never touches skb_shinfo()->flags; skb_shift() moves frag\ndescriptors directly and leaves flags untouched.  As a result, the\ndestination skb keeps a reference to the same externally-owned or\npage-cache-backed pages while reporting skb_has_shared_frag() as\nfalse.\n\nThe mismatch is harmful in any in-place writer that uses\nskb_has_shared_frag() to decide whether shared pages must be detoured\nthrough skb_cow_data().  ESP input is one such writer (esp4.c,\nesp6.c), and a single nft 'dup to <local>' rule -- or any other\nnf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d\nskb in esp_input() with the marker stripped, letting an unprivileged\nuser write into the page cache of a root-owned read-only file via\nauthencesn-ESN stray writes.\n\nSet SKBFL_SHARED_FRAG on the destination whenever frag descriptors\nwere actually moved from the source.  skb_copy() and skb_copy_expand()\nshare skb_copy_header() too but linearize all paged data into freshly\nallocated head storage and emerge with nr_frags == 0, so\nskb_has_shared_frag() returns false on its own; they need no change.\n\nThe same omission exists in skb_gro_receive() and skb_gro_receive_list().\nThe former moves the incoming skb's frag descriptors into the\naccumulator's last sub-skb via two paths (a direct frag-move loop and\nthe head_frag + memcpy path); the latter chains the incoming skb whole\nonto p's frag_list.  Downstream skb_segment() reads only\nskb_shinfo(p)->flags, and skb_segment_list() reuses each sub-skb's\nshinfo as the nskb -- both p and lp must carry the marker.\n\nThe same omission also exists in tcp_clone_payload(), which builds an\nMTU probe skb by moving frag descriptors from skbs on sk_write_queue\ninto a freshly allocated nskb.  The helper falls into the same family\nand warrants the same fix for consistency; no TCP TX-side in-place\nwriter is currently known to reach a user page through this gap, but\na future consumer depending on the marker would regress silently.\n\nThe same omission exists in skb_segment(): the per-iteration flag\nmerge takes only head_skb's flag, and the inner switch that rebinds\nfrag_skb to list_skb on head_skb-frags exhaustion does not fold the\nnew frag_skb's flag into nskb.  Fold frag_skb's flag at both sites\nso segments drawing frags from frag_list members carry the marker."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-23T13:20:26.042Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/fbeab9555564a1b98e8582cd106dfe46c4606991"
        },
        {
          "url": "https://git.kernel.org/stable/c/179f1852bdedc300e373e807cc102cd81feff196"
        },
        {
          "url": "https://git.kernel.org/stable/c/12401fcfb01f53ccc63ab0a3246570fe8f3105ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/989214c66884d70716d83dc1d0bf5e16287bf349"
        },
        {
          "url": "https://git.kernel.org/stable/c/fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8"
        },
        {
          "url": "https://git.kernel.org/stable/c/ff375cc75f9167168db38e0464a482d5fbc8d81d"
        },
        {
          "url": "https://git.kernel.org/stable/c/9bc9d6d6967a2239aa57af2aa53554eddd640d20"
        }
      ],
      "title": "net: skbuff: propagate shared-frag marker through frag-transfer helpers",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43503",
    "datePublished": "2026-05-23T11:44:01.103Z",
    "dateReserved": "2026-05-01T14:12:56.014Z",
    "dateUpdated": "2026-05-23T13:20:26.042Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}