{"api_version":"1","generated_at":"2026-11-04T05:40:49+00:00","cve":"CVE-2026-98374","urls":{"html":"https://cve.report/CVE-2026-98374","api":"https://cve.report/api/cve/CVE-2026-98374.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98374","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98374"},"summary":{"title":"tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp->highest_sack.\ntp->retransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-07 13:17:23","updated_at":"2026-10-24 14:16:39"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","data":{"baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b","name":"https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97","name":"https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd","name":"https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018","name":"https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e","name":"https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f","name":"https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4","name":"https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98374","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98374","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c31b70c9968fe9c4194d1b5d06d07596a3b680de fad6d429651e748365e93ca54645accc212f0018 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c31b70c9968fe9c4194d1b5d06d07596a3b680de c5b4da1f403a658c1c19766be2b426003ada419f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c31b70c9968fe9c4194d1b5d06d07596a3b680de 71d45049b0d631dfdbf3c65305f7fca676de023b git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c31b70c9968fe9c4194d1b5d06d07596a3b680de e3ea71cb1408a013ed4e8a757b815f1a919324bd git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c31b70c9968fe9c4194d1b5d06d07596a3b680de 631aa4cb45099f09e9385dd786bd291c6270bfc4 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c31b70c9968fe9c4194d1b5d06d07596a3b680de 0f87720c7e4bcab07c24888b3cf12bfe857bb90e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected c31b70c9968fe9c4194d1b5d06d07596a3b680de fe99bbeee5c5dbd3abc30721a8079ced59649d97 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.11","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.11 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.222 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.189 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.158 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.112 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.55 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.9 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/ipv4/tcp_output.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"fad6d429651e748365e93ca54645accc212f0018","status":"affected","version":"c31b70c9968fe9c4194d1b5d06d07596a3b680de","versionType":"git"},{"lessThan":"c5b4da1f403a658c1c19766be2b426003ada419f","status":"affected","version":"c31b70c9968fe9c4194d1b5d06d07596a3b680de","versionType":"git"},{"lessThan":"71d45049b0d631dfdbf3c65305f7fca676de023b","status":"affected","version":"c31b70c9968fe9c4194d1b5d06d07596a3b680de","versionType":"git"},{"lessThan":"e3ea71cb1408a013ed4e8a757b815f1a919324bd","status":"affected","version":"c31b70c9968fe9c4194d1b5d06d07596a3b680de","versionType":"git"},{"lessThan":"631aa4cb45099f09e9385dd786bd291c6270bfc4","status":"affected","version":"c31b70c9968fe9c4194d1b5d06d07596a3b680de","versionType":"git"},{"lessThan":"0f87720c7e4bcab07c24888b3cf12bfe857bb90e","status":"affected","version":"c31b70c9968fe9c4194d1b5d06d07596a3b680de","versionType":"git"},{"lessThan":"fe99bbeee5c5dbd3abc30721a8079ced59649d97","status":"affected","version":"c31b70c9968fe9c4194d1b5d06d07596a3b680de","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/ipv4/tcp_output.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.11"},{"lessThan":"5.11","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.222","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.189","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.158","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.112","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.55","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.222","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.189","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.158","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.112","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.55","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.9","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"5.11","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp->highest_sack.\ntp->retransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy."}],"metrics":[{"cvssV3_1":{"baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:N - A malicious IPv4 peer supplies fragmentation-needed ICMP messages quoting the client's TFO SYN and an ACK-less crossed TCP SYN; ip_rcv() dispatches these through tcp_v4_err() and tcp_rcv_state_process() to the patched tcp_send_synack().\nAC:L - After the victim's TFO send, the peer controls packet ordering: ICMP makes tcp_simple_retransmit() cache and clone the SYN, then the crossed SYN makes tcp_send_synack() free it; a later PMTU event dereferences the stale hint without requiring a race or external failure.\nPR:N - The ordinary TCP and ICMP paths require only a matching tuple and quoted sequence, not authentication or target privileges; a peer that received the TFO SYN knows the values checked by tcp_v4_err() and the TCP socket lookup.\nUI:R - A victim-side process must issue sendmsg(MSG_FASTOPEN) with data and a usable cookie or no-cookie mode to establish tp->syn_data in TCP_SYN_SENT; remote packets alone cannot construct this vulnerable retransmit queue state.\nS:U - The freed skb, retransmit tree, and subsequent stale accesses all belong to the same host kernel TCP security authority; tcp_send_synack() does not cross a VM, IOMMU, or sandbox boundary.\nC:H - retransmit_skb_hint retains a freed skbuff_fclone_cache address, and tcp_verify_retransmit_hint() reads its TCP control block while tcp_xmit_retransmit_queue() follows its rbnode links, permitting attacker-influenced stale-object reads after slab reuse.\nI:H - tcp_xmit_retransmit_queue() can treat the reclaimed object as a live skb and pass it into retransmission code that modifies skb control and header state; attacker-shaped reuse of the stale rbnode and skb fields makes this UAF exploitable for kernel memory corruption.\nA:H - The demonstrated stale TCP_SKB_CB read already triggers KASAN in tcp_mark_skb_lost(), while using the freed object as an rbtree-walk root can dereference invalid links and cause a kernel oops or panic."}]}],"providerMetadata":{"dateUpdated":"2026-10-24T14:08:34.914Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/fad6d429651e748365e93ca54645accc212f0018"},{"url":"https://git.kernel.org/stable/c/c5b4da1f403a658c1c19766be2b426003ada419f"},{"url":"https://git.kernel.org/stable/c/71d45049b0d631dfdbf3c65305f7fca676de023b"},{"url":"https://git.kernel.org/stable/c/e3ea71cb1408a013ed4e8a757b815f1a919324bd"},{"url":"https://git.kernel.org/stable/c/631aa4cb45099f09e9385dd786bd291c6270bfc4"},{"url":"https://git.kernel.org/stable/c/0f87720c7e4bcab07c24888b3cf12bfe857bb90e"},{"url":"https://git.kernel.org/stable/c/fe99bbeee5c5dbd3abc30721a8079ced59649d97"}],"title":"tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98374","datePublished":"2026-10-07T13:01:48.600Z","dateReserved":"2026-09-25T10:25:14.345Z","dateUpdated":"2026-10-24T14:08:34.914Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-07 13:17:23","lastModifiedDate":"2026-10-24 14:16:39","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98374","Ordinal":"1","Title":"tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synac","CVE":"CVE-2026-98374","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98374","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free of retransmit_skb_hint in tcp_send_synack()\n\nWhen tcp_send_synack() replaces the cloned SYN skb at the head of the\nretransmit queue with a copy, it frees the original with\ntcp_rtx_queue_unlink_and_free() and only repairs tp->highest_sack.\ntp->retransmit_skb_hint keeps pointing at the freed\nskbuff_fclone_cache object.\n\nThe dangling hint is read in tcp_verify_retransmit_hint() and used as\nthe root of the rbtree walk in tcp_xmit_retransmit_queue().  An\nunprivileged TFO client (sendmsg(MSG_FASTOPEN)) can arm the hint with\nan attacker-supplied ICMP fragmentation-needed message, after which a\nsimultaneous open frees the armed SYN skb:\n\n  BUG: KASAN: slab-use-after-free in tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n  Read of size 4 at addr ffff88800604d928 by task swapper/1/0\n  Call Trace:\n   tcp_mark_skb_lost (net/ipv4/tcp_input.c:1316)\n   tcp_simple_retransmit (net/ipv4/tcp_input.c:3158)\n   tcp_v4_err (net/ipv4/tcp_ipv4.c:587)\n\nSync the hint to the copy.","Type":"Description","Title":"tcp: fix use-after-free of retransmit_skb_hint in tcp_send_synac"}]}}}