--- id: CVE-2026-74714 title: |- In the Linux kernel, the following vulnerability has been resolved: bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch() reqsk_queue_hash_req() publishes a TCP_NEW_SYN_RECV request_sock onto the ehash chain, drops the bucke… summary: |- In the Linux kernel, the following vulnerability has been resolved: bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch() reqsk_queue_hash_req() publishes a TCP_NEW_SYN_RECV request_sock onto the ehash chain, drops the bucke… severity: high cvss: 7.8 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-416 vendor: Linux product: Linux affected: - >- Linux >= 04c7820b776f1c4b48698574c47de9e940d368e8 < cc0295f89296ed351fc4b0b48fee887ba02c5d24 - >- Linux >= 04c7820b776f1c4b48698574c47de9e940d368e8 < ddbe966b5d1fe212ada749bc3d0b410f1a7dea74 - >- Linux >= 04c7820b776f1c4b48698574c47de9e940d368e8 < 7d2b60a4bc0499f62ff8520af6309bbe170882fd - >- Linux >= 04c7820b776f1c4b48698574c47de9e940d368e8 < cefcbbe20846a45f9a7dae868f7ef1000953e2df - >- Linux >= 04c7820b776f1c4b48698574c47de9e940d368e8 < 97e74d3e45d653c07c2d406fc530a9bbe3df8396 - >- Linux >= 04c7820b776f1c4b48698574c47de9e940d368e8 < e5fd3f514e27db1f05fbd72ba615d74941e23c51 - Linux 5.15 published: '2026-08-22' updated: '2026-10-16' sourceUpdated: '2026-10-16T20:17:54.033' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-74714' references: - url: 'https://git.kernel.org/stable/c/7d2b60a4bc0499f62ff8520af6309bbe170882fd' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/97e74d3e45d653c07c2d406fc530a9bbe3df8396' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/cc0295f89296ed351fc4b0b48fee887ba02c5d24' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/cefcbbe20846a45f9a7dae868f7ef1000953e2df' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/ddbe966b5d1fe212ada749bc3d0b410f1a7dea74' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/e5fd3f514e27db1f05fbd72ba615d74941e23c51' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74714.json - url: 'https://access.redhat.com/security/cve/CVE-2026-74714' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2521378' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-74714' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-74714' - url: 'https://kernelcve.org/list/?q=CVE-2026-74714' - url: >- https://lore.kernel.org/linux-cve-announce/2026082238-CVE-2026-74714-2ea9@gregkh/T tags: - nvd - cve.org - csaf - vex - red-hat - score-dispute epss: 0.00126 epssPercentile: 0.02238 ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-10-16T19:15:26.338787Z' scores: nvd: 7.8 vendor: 4.7 ingestedAt: '2026-10-14T13:30:58.545Z' --- ## Overview In the Linux kernel, the following vulnerability has been resolved: bpf: tcp: Fix use-after-free in bpf_iter_tcp_established_batch() reqsk_queue_hash_req() publishes a TCP_NEW_SYN_RECV request_sock onto the ehash chain, drops the bucket lock, and only afterwards sets rsk_refcnt to 3. Lockless readers such as __inet_lookup_established() handle this with refcount_inc_not_zero(), but bpf_iter_tcp_established_batch() uses plain sock_hold() while holding the bucket lock, on the assumption that the lock guarantees sk_refcnt > 0. That assumption does not hold for request_sock: CPU 0 CPU 1 ----- ----- tcp_conn_request() reqsk_queue_hash_req() inet_ehash_insert(req) spin_lock(bucket) __sk_nulls_add_node_rcu(req) // rsk_refcnt == 0 spin_unlock(bucket) bpf_iter_tcp_established_batch() spin_lock(bucket) sock_hold(req) <-- addition on 0 spin_unlock(bucket) refcount_set(&req->rsk_refcnt, 3) // clobbers saturated value which surfaces as: refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x48/0x90, CPU#1 Call Trace: bpf_iter_tcp_established_batch+0x14e/0x170 bpf_iter_tcp_batch+0x53/0x200 bpf_iter_tcp_seq_next+0x27/0x70 bpf_seq_read+0x107/0x410 vfs_read+0xb9/0x380 The iterator's stolen reference is lost when the publishing CPU's refcount_set() overwrites the count, leaving the socket one reference short. When the last legitimate owner drops its reference the reqsk is freed while still reachable, leading to use-after-free. This reproduces in seconds with tcp_syncookies=0, a handful of threads doing connect()/close() to a local listener while others read an iter/tcp link in a tight loop. Use refcount_inc_not_zero() and skip the socket on failure. A skipped socket is still part of the bucket, so keep counting it in expected. The reallocations are sized from expected, and a request sock whose refcount gets published while the lock is held across the last realloc must already have room. A skipped socket is counted in expected but never batched, so end_sk can be short of expected on a batch that is actually complete. Decide completeness by whether the walk left any socket behind instead. The WARN after the locked realloc checks the same, replacing an end_sk == expected check that could not hold on that path since commit cdec67a489d4 ("bpf: tcp: Make sure iter->batch always contains a full bucket snapshot"). If every matching socket in a bucket is mid-init (refcount 0), end_sk stays 0. Advance to the next bucket rather than returning a batch entry that was never filled this round. ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-10-26 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74714.json)