{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-43503", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-43503", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-05-23T11:44:01.103Z", "updatedAt": "2026-10-16T18:44:47.794Z", "importedAt": "2026-10-24T01:58:14.884Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "net: skbuff: propagate shared-frag marker through frag-transfer helpers", "summary": "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 ' 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.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "fbeab9555564a1b98e8582cd106dfe46c4606991" }, { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "179f1852bdedc300e373e807cc102cd81feff196" }, { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "12401fcfb01f53ccc63ab0a3246570fe8f3105ee" }, { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "989214c66884d70716d83dc1d0bf5e16287bf349" }, { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8" }, { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "ff375cc75f9167168db38e0464a482d5fbc8d81d" }, { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "9bc9d6d6967a2239aa57af2aa53554eddd640d20" }, { "version": "cef401de7be8c4e155c6746bfccf721a4fa5fab9", "status": "affected", "versionType": "git", "lessThan": "48f6a5356a33dd78e7144ae1faef95ffc990aae0" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "3.9", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "3.9" }, { "version": "5.10.257", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.208", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.174", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.141", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.91", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.33", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.0.10", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.0.*" }, { "version": "7.1", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }