{"id":"CVE-2025-40186","revision":null,"records":[{"revision":"7b54ad20bf66492984cf19162a0f83ba","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2025-40186","aliases":[],"title":"tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().\n\nsyzbot reported the splat below in tcp_conn_request(). [0]\n\nIf a listener is close()d while a TFO socket is being processed in\ntcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk\nand calls inet_child_forget(), which calls tcp_disconnect() for the\nTFO socket.\n\nAfter the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(),\nwhere reqsk_put() is called due to !reqsk->sk.\n\nThen, reqsk_fastopen_remove() in tcp_conn_request() decrements the\nlast req->rsk_refcnt and frees reqsk, and __reqsk_free() at the\ndrop_and_free label causes the refcount underflow for the listener\nand double-free of the reqsk.\n\nLet's remove reqsk_fastopen_remove() in tcp_conn_request().\n\nNote that other callers make sure tp->fastopen_rsk is not NULL.\n\n[0]:\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 12 PID: 5563 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28)\nModules linked in:\nCPU: 12 UID: 0 PID: 5563 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025\nRIP: 0010:refcount_warn_saturate (lib/refcount.c:28)\nCode: ab e8 8e b4 98 ff 0f 0b c3 cc cc cc cc cc 80 3d a4 e4 d6 01 00 75 9c c6 05 9b e4 d6 01 01 48 c7 c7 e8 df fb ab e8 6a b4 98 ff <0f> 0b e9 03 5b 76 00 cc 80 3d 7d e4 d6 01 00 0f 85 74 ff ff ff c6\nRSP: 0018:ffffa79fc0304a98 EFLAGS: 00010246\nRAX: d83af4db1c6b3900 RBX: ffff9f65c7a69020 RCX: d83af4db1c6b3900\nRDX: 0000000000000000 RSI: 00000000ffff7fff RDI: ffffffffac78a280\nRBP: 000000009d781b60 R08: 0000000000007fff R09: ffffffffac6ca280\nR10: 0000000000017ffd R11: 0000000000000004 R12: ffff9f65c7b4f100\nR13: ffff9f65c7d23c00 R14: ffff9f65c7d26000 R15: ffff9f65c7a64ef8\nFS: 00007f9f962176c0(0000) GS:ffff9f65fcf00000(0000) knlGS:0000000000000000\nCS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 0000200000000180 CR3: 000000000dbbe006 CR4: 0000000000372ef0\nCall Trace:\n \n tcp_conn_request (./include/linux/refcount.h:400 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 ./include/net/sock.h:1965 ./include/net/request_sock.h:131 net/ipv4/tcp_input.c:7301)\n tcp_rcv_state_process (net/ipv4/tcp_input.c:6708)\n tcp_v6_do_rcv (net/ipv6/tcp_ipv6.c:1670)\n tcp_v6_rcv (net/ipv6/tcp_ipv6.c:1906)\n ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:438)\n ip6_input (net/ipv6/ip6_input.c:500)\n ipv6_rcv (net/ipv6/ip6_input.c:311)\n __netif_receive_skb (net/core/dev.c:6104)\n process_backlog (net/core/dev.c:6456)\n __napi_poll (net/core/dev.c:7506)\n net_rx_action (net/core/dev.c:7569 net/core/dev.c:7696)\n handle_softirqs (kernel/softirq.c:579)\n do_softirq (kernel/softirq.c:480)\n ","state":0,"publishedAt":"2025-11-12T21:56:29.033+00:00","modifiedAt":"2026-10-15T22:02:39.982+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"net/ipv4/tcp_input.c\"\n ],\n \"versions\": [\n {\n \"version\": \"7ec092a91ff351dcde89c23e795b73a328274db6\",\n \"lessThan\": \"e359b742eac1eac75cff4e38ee2e8cea492acd9b\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"a4378dedd6e07e62f2fccb17d78c9665718763d0\",\n \"lessThan\": \"ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"33a4fdf0b4a25f8ce65380c3b0136b407ca57609\",\n \"lessThan\": \"eb85ad5f23268d64b037bfb545cbcba3752f90c7\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"17d699727577814198d744d6afe54735c6b54c99\",\n \"lessThan\": \"643a94b0cf767325e953591c212be2eb826b9d7f\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"dfd06131107e7b699ef1e2a24ed2f7d17c917753\",\n \"lessThan\": \"422c1c173c39bbbae1e0eaaf8aefe40b2596233b\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"fa4749c065644af4db496b338452a69a3e5147d9\",\n \"lessThan\": \"c11ace909e873118295e9eb22dc8c58b0b50eb32\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01\",\n \"lessThan\": \"64dc47a13aa3d9daf7cec29b44dca8e22a6aea15\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01\",\n \"lessThan\": \"2e7cbbbe3d61c63606994b7ff73c72537afe2e1c\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"ae313d14b45eca7a6bb29cb9bf396d977e7d28fb\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5.4.300\",\n \"lessThan\": \"5.4.301\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.245\",\n \"lessThan\": \"5.10.246\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.194\",\n \"lessThan\": \"5.15.195\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.154\",\n \"lessThan\": \"6.1.157\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.108\",\n \"lessThan\": \"6.6.113\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.49\",\n \"lessThan\": \"6.12.54\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.16.9\",\n \"lessThan\": \"6.17\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"net/ipv4/tcp_input.c\"\n ],\n \"versions\": [\n {\n \"version\": \"6.17\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"6.17\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.4.301\",\n \"lessThanOrEqual\": \"5.4.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.246\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.195\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.157\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.113\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.54\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.17.4\",\n \"lessThanOrEqual\": \"6.17.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","score":8.1,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/e359b742eac1eac75cff4e38ee2e8cea492acd9b","https://git.kernel.org/stable/c/ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d","https://git.kernel.org/stable/c/eb85ad5f23268d64b037bfb545cbcba3752f90c7","https://git.kernel.org/stable/c/643a94b0cf767325e953591c212be2eb826b9d7f","https://git.kernel.org/stable/c/422c1c173c39bbbae1e0eaaf8aefe40b2596233b","https://git.kernel.org/stable/c/c11ace909e873118295e9eb22dc8c58b0b50eb32","https://git.kernel.org/stable/c/64dc47a13aa3d9daf7cec29b44dca8e22a6aea15","https://git.kernel.org/stable/c/2e7cbbbe3d61c63606994b7ff73c72537afe2e1c"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-40186","license":"CVE Program Terms of Use","key":"cve-program:CVE-2025-40186","identifiers":["CVE-2025-40186"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all 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Missing entries do not establish absence of exploitation.","generation":"2026-11-09T12:02:21.9910047+00:00","complete":true,"records":1769,"lastAttemptAt":"2026-11-09T12:02:21.9910047+00:00","lastSuccessAt":"2026-11-09T12:02:22.1773794+00:00","error":null,"lastVerifiedAt":"2026-11-09T12:02:22.1773831+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"cve-program","scope":"Official CVE Program baseline and cumulative hourly delta; all vendors, published and rejected records","generation":"cve-24e6fde7b744113daefb8f6135035fb8a5c69c9617c9c0d40574a0376532ffd3-bc5670b92e6417137e6d98178f734a585c0efdac3c24cdab996a156ba398735b","complete":true,"records":421397,"lastAttemptAt":"2026-11-09T12:02:16.4943065+00:00","lastSuccessAt":"2026-11-09T12:02:16.4102763+00:00","error":null,"lastVerifiedAt":"2026-11-09T12:02:16.4943065+00:00","snapshotPublishedAt":"2026-11-09T11:21:04+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"euvd","scope":"Rolling EUVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. 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