{"schema":"threatline.record/2","record":{"id":"CVE-2026-43503","aliases":[],"summary":"net: skbuff: propagate shared-frag marker through frag-transfer helpers","details":"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.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","source_modified_at":"2026-10-16T18:44:47.794Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"Linux","vendor":"Linux","versions":[{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"fbeab9555564a1b98e8582cd106dfe46c4606991","status":"affected","versionType":"git"},{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"179f1852bdedc300e373e807cc102cd81feff196","status":"affected","versionType":"git"},{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"12401fcfb01f53ccc63ab0a3246570fe8f3105ee","status":"affected","versionType":"git"},{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"989214c66884d70716d83dc1d0bf5e16287bf349","status":"affected","versionType":"git"},{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8","status":"affected","versionType":"git"},{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"ff375cc75f9167168db38e0464a482d5fbc8d81d","status":"affected","versionType":"git"},{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"9bc9d6d6967a2239aa57af2aa53554eddd640d20","status":"affected","versionType":"git"},{"version":"cef401de7be8c4e155c6746bfccf721a4fa5fab9","lessThan":"48f6a5356a33dd78e7144ae1faef95ffc990aae0","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","source_modified_at":"2026-10-16T18:44:47.794Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"Linux","vendor":"Linux","versions":[{"version":"3.9","status":"affected"},{"version":"0","lessThan":"3.9","status":"unaffected","versionType":"semver"},{"version":"5.10.257","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.208","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.174","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.141","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.91","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.33","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.0.10","lessThanOrEqual":"7.0.*","status":"unaffected","versionType":"semver"},{"version":"7.1","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","source_modified_at":"2026-10-16T18:44:47.794Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"Linux","ecosystem":null},"version":"179f1852bdedc300e373e807cc102cd81feff196","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","source_modified_at":"2026-10-16T18:44:47.794Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"Linux","ecosystem":null},"version":"12401fcfb01f53ccc63ab0a3246570fe8f3105ee","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","source_modified_at":"2026-10-16T18:44:47.794Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"Linux","ecosystem":null},"version":"989214c66884d70716d83dc1d0bf5e16287bf349","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","source_modified_at":"2026-10-16T18:44:47.794Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"Linux","ecosystem":null},"version":"9bc9d6d6967a2239aa57af2aa53554eddd640d20","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","source_modified_at":"2026-10-16T18:44:47.794Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"Linux","ecosystem":null},"version":"48f6a5356a33dd78e7144ae1faef95ffc990aae0","basis":"first unaffected version stated in the CVE record"}],"cvss":8.8,"severity":"High","kev":{"listed":false},"epss":{"probability":0.01987,"percentile":0.80479,"score_date":"2026-10-23"},"published_at":"2026-05-23T11:44:01.103Z","modified_at":"2026-10-16T18:44:47.794Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-43503","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-16T18:44:47.794Z"},{"source":"Metasploit","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/local/dirtyclone_cve_2026_43503.rb","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-05-21"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-43503","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","Metasploit","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/fbeab9555564a1b98e8582cd106dfe46c4606991"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/179f1852bdedc300e373e807cc102cd81feff196"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/12401fcfb01f53ccc63ab0a3246570fe8f3105ee"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/989214c66884d70716d83dc1d0bf5e16287bf349"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/fc6eb39c55e97df2f94ad974b8a5bbcd019da2c8"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/ff375cc75f9167168db38e0464a482d5fbc8d81d"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/9bc9d6d6967a2239aa57af2aa53554eddd640d20"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/48f6a5356a33dd78e7144ae1faef95ffc990aae0"},{"source":"CVE List","url":"https://access.redhat.com/security/cve/CVE-2026-43503","tags":["vdb-entry","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2480902","tags":["issue-tracking","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43503.json","tags":["x_sadp-csaf-vex"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19540","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:33486","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:21695","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:21690","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:23233","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:20087","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:25044","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:21656","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:23245","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:21702","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:23240","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:20299","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19569","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19705","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:20593","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:20054","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:20129","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19568","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19666","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:23470","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:20130","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:20051","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19521","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:23471","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:23469","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:24814","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:23468","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19664","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19711","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://access.redhat.com/errata/RHSA-2026:19875","tags":["vendor-advisory","x_refsource_REDHAT"]},{"source":"CVE List","url":"https://cert-portal.siemens.com/productcert/html/ssa-784472.html"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"total","assessed_at":"2026-10-16T18:43:03.458762Z"},"exploits":[{"added":"2026-10-09","check":true,"date":"2026-05-21","kind":"Exploit module","name":"Linux Kernel DirtyClone Local Privilege Escalation","source":"Metasploit","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/linux/local/dirtyclone_cve_2026_43503.rb"}],"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-16T18:44:47.794Z","content_hash":"5ce8536560e6f9c59b5f19f5e3a36c50b75cbaab0d5db7a8e9f4c31a5ba8073b"}}