{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98374", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.345Z", "datePublished": "2026-10-07T13:01:48.600Z", "dateUpdated": "2026-10-24T14:08:34.914Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:08:34.914Z" }, "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": { "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" }, "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/tcp_output.c" ], "versions": [ { "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de", "lessThan": "fad6d429651e748365e93ca54645accc212f0018", "status": "affected", "versionType": "git" }, { "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de", "lessThan": "c5b4da1f403a658c1c19766be2b426003ada419f", "status": "affected", "versionType": "git" }, { "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de", "lessThan": "71d45049b0d631dfdbf3c65305f7fca676de023b", "status": "affected", "versionType": "git" }, { "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de", "lessThan": "e3ea71cb1408a013ed4e8a757b815f1a919324bd", "status": "affected", "versionType": "git" }, { "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de", "lessThan": "631aa4cb45099f09e9385dd786bd291c6270bfc4", "status": "affected", "versionType": "git" }, { "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de", "lessThan": "0f87720c7e4bcab07c24888b3cf12bfe857bb90e", "status": "affected", "versionType": "git" }, { "version": "c31b70c9968fe9c4194d1b5d06d07596a3b680de", "lessThan": "fe99bbeee5c5dbd3abc30721a8079ced59649d97", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/tcp_output.c" ], "versions": [ { "version": "5.11", "status": "affected" }, { "version": "0", "lessThan": "5.11", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.222", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.189", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.158", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.112", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.55", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.9", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.222" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.1.189" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.12.112" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.18.55" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "7.2.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "7.3" } ] } ] } ], "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" } } } }