{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74714", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.928Z", "datePublished": "2026-08-22T15:33:09.643Z", "dateUpdated": "2026-10-16T19:16:11.358Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-25T05:41:57.341Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch()\n\nreqsk_queue_hash_req() publishes a TCP_NEW_SYN_RECV request_sock onto\nthe ehash chain, drops the bucket lock, and only afterwards sets\nrsk_refcnt to 3.\n\nLockless readers such as __inet_lookup_established() handle this with\nrefcount_inc_not_zero(), but bpf_iter_tcp_established_batch() uses plain\nsock_hold() while holding the bucket lock, on the assumption that the\nlock guarantees sk_refcnt > 0. That assumption does not hold for\nrequest_sock:\n\n CPU 0 CPU 1\n ----- -----\n tcp_conn_request()\n reqsk_queue_hash_req()\n inet_ehash_insert(req)\n spin_lock(bucket)\n __sk_nulls_add_node_rcu(req) // rsk_refcnt == 0\n spin_unlock(bucket)\n bpf_iter_tcp_established_batch()\n spin_lock(bucket)\n sock_hold(req) <-- addition on 0\n spin_unlock(bucket)\n refcount_set(&req->rsk_refcnt, 3) // clobbers saturated value\n\nwhich surfaces as:\n\n refcount_t: addition on 0; use-after-free.\n WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x48/0x90, CPU#1\n Call Trace:\n bpf_iter_tcp_established_batch+0x14e/0x170\n bpf_iter_tcp_batch+0x53/0x200\n bpf_iter_tcp_seq_next+0x27/0x70\n bpf_seq_read+0x107/0x410\n vfs_read+0xb9/0x380\n\nThe iterator's stolen reference is lost when the publishing CPU's\nrefcount_set() overwrites the count, leaving the socket one reference\nshort. When the last legitimate owner drops its reference the reqsk is\nfreed while still reachable, leading to use-after-free.\n\nThis reproduces in seconds with tcp_syncookies=0, a handful of threads\ndoing connect()/close() to a local listener while others read an\niter/tcp link in a tight loop.\n\nUse refcount_inc_not_zero() and skip the socket on failure. A skipped\nsocket is still part of the bucket, so keep counting it in expected.\nThe reallocations are sized from expected, and a request sock whose\nrefcount gets published while the lock is held across the last realloc\nmust already have room.\n\nA skipped socket is counted in expected but never batched, so end_sk\ncan be short of expected on a batch that is actually complete. Decide\ncompleteness by whether the walk left any socket behind instead. The\nWARN after the locked realloc checks the same, replacing an\nend_sk == expected check that could not hold on that path since\ncommit cdec67a489d4 (\"bpf: tcp: Make sure iter->batch always\ncontains a full bucket snapshot\").\n\nIf every matching socket in a bucket is mid-init (refcount 0), end_sk\nstays 0. Advance to the next bucket rather than returning a batch entry\nthat was never filled this round." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - bpf_iter_tcp_established_batch() is reached only via local bpf() to load a BPF_TRACE_ITER TCP program, create an iterator link/fd, and read() it (bpf_seq_read->bpf_iter_tcp_batch); per kernel CNA guidance BPF iterator paths are Local even though concurrent TCP_NEW_SYN_RECV creation can be driven by network SYNs.\nAC:L - The fix commit reproduces in seconds with threads doing connect()/close() while others read iter/tcp in a tight loop; the attacker controls both the BPF iterator and TCP connection churn, so the refcount race between sock_hold() and refcount_set() is reliably winnable without uncontrollable victim state.\nPR:L - Loading BPF_PROG_TYPE_TRACING/BPF_TRACE_ITER requires CAP_BPF and CAP_PERFMON at bpf_prog_load(); per kernel CNA guidance these are Low privileges because BPF tokens and user namespaces can delegate them to non-init-namespace users, not only real root.\nUI:N - No victim interaction is required; the attacker loads their own iter/tcp BPF program and link, then triggers the race with self-generated connect/close traffic or SYN activity to listeners in the iterated network namespace.\nS:U - Impact is a kernel heap use-after-free and memory corruption within the same host kernel security authority; this is standard local kernel compromise/crash, not a VM escape, sandbox boundary cross, or IOMMU bypass.\nC:H - The iterator retains dangling request_sock pointers after refcount_set() clobbers a sock_hold() taken on sk_refcnt==0; subsequent bpf_iter_tcp_seq_show/put_batch dereference freed kernel objects, giving UAF read primitives per kernel CNA UAF guidance.\nI:H - Freed request_sock slabs can be reallocated while the iterator batch still references them; UAF enables corrupted socket metadata, refcount abuse, and control-flow hijacking via heap grooming, meeting High integrity under kernel CNA memory-corruption guidance.\nA:H - The bug surfaces as refcount_warn_saturate and leaves the reqsk one reference short so it is freed while still reachable from the iterator batch, causing kernel oops/panic; the tight-loop repro shows reliable, repeatable host denial of service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/tcp_ipv4.c" ], "versions": [ { "version": "04c7820b776f1c4b48698574c47de9e940d368e8", "lessThan": "cc0295f89296ed351fc4b0b48fee887ba02c5d24", "status": "affected", "versionType": "git" }, { "version": "04c7820b776f1c4b48698574c47de9e940d368e8", "lessThan": "ddbe966b5d1fe212ada749bc3d0b410f1a7dea74", "status": "affected", "versionType": "git" }, { "version": "04c7820b776f1c4b48698574c47de9e940d368e8", "lessThan": "7d2b60a4bc0499f62ff8520af6309bbe170882fd", "status": "affected", "versionType": "git" }, { "version": "04c7820b776f1c4b48698574c47de9e940d368e8", "lessThan": "cefcbbe20846a45f9a7dae868f7ef1000953e2df", "status": "affected", "versionType": "git" }, { "version": "04c7820b776f1c4b48698574c47de9e940d368e8", "lessThan": "97e74d3e45d653c07c2d406fc530a9bbe3df8396", "status": "affected", "versionType": "git" }, { "version": "04c7820b776f1c4b48698574c47de9e940d368e8", "lessThan": "e5fd3f514e27db1f05fbd72ba615d74941e23c51", "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_ipv4.c" ], "versions": [ { "version": "5.15", "status": "affected" }, { "version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.183", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.152", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.104", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.45", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.9", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "5.15", "versionEndExcluding": "6.1.183" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.6.152" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.104" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.18.45" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "7.1.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/cc0295f89296ed351fc4b0b48fee887ba02c5d24" }, { "url": "https://git.kernel.org/stable/c/ddbe966b5d1fe212ada749bc3d0b410f1a7dea74" }, { "url": "https://git.kernel.org/stable/c/7d2b60a4bc0499f62ff8520af6309bbe170882fd" }, { "url": "https://git.kernel.org/stable/c/cefcbbe20846a45f9a7dae868f7ef1000953e2df" }, { "url": "https://git.kernel.org/stable/c/97e74d3e45d653c07c2d406fc530a9bbe3df8396" }, { "url": "https://git.kernel.org/stable/c/e5fd3f514e27db1f05fbd72ba615d74941e23c51" } ], "title": "bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-74714", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:15:26.338787Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:16:11.358Z" } } ] } }