CVE-2026-64435 (GCVE-0-2026-64435)
Vulnerability from cvelistv5
Published
2026-07-25 08:51
Modified
2026-08-17 04:55
Severity ?
8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: audit: Fix data races of skb_queue_len() readers on audit_queue Multiple readers access audit_queue.qlen via skb_queue_len() without holding the queue lock or using READ_ONCE(), while kauditd writes to this field via the skb_dequeue() → __skb_unlink() path with WRITE_ONCE() protected by a spinlock. This constitutes data races. All affected skb_queue_len(&audit_queue) call sites: - kauditd_thread() wait_event_freezable() condition - audit_receive_msg() AUDIT_GET handler (s.backlog assignment) - audit_receive() backlog check - audit_log_start() backlog check and pr_warn() KCSAN reports the following conflicting access pattern (one example): ================================================================== BUG: KCSAN: data-race in audit_log_start / skb_dequeue write (marked) to 0xffffffff8512ee20 of 4 bytes by task 661 on cpu 57: skb_dequeue+0x70/0xf0 kauditd_send_queue+0x71/0x220 kauditd_thread+0x1cb/0x430 kthread+0x1c2/0x210 ret_from_fork+0x162/0x1a0 ret_from_fork_asm+0x1a/0x30 read to 0xffffffff8512ee20 of 4 bytes by task 36586 on cpu 1: audit_log_start+0x2a0/0x6b0 audit_core_dumps+0x64/0xa0 do_coredump+0x14b/0x1260 get_signal+0xeb2/0xf70 arch_do_signal_or_restart+0x41/0x170 exit_to_user_mode_loop+0xa2/0x1c0 do_syscall_64+0x1a3/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0xe0 value changed: 0x00000001 -> 0x00000000 ================================================================== Resolve the race by switching to lockless helper skb_queue_len_lockless(), which internally uses READ_ONCE() and properly pairs with the WRITE_ONCE() write accesses already present on the writer side. [PM: line length tweak]
References
Impacted products
Vendor Product Version
Linux Linux Version: 3197542482df22c2a131d4a813280bd7c54cedf5
Version: 3197542482df22c2a131d4a813280bd7c54cedf5
Version: 3197542482df22c2a131d4a813280bd7c54cedf5
Version: 3197542482df22c2a131d4a813280bd7c54cedf5
Version: 3197542482df22c2a131d4a813280bd7c54cedf5
Version: 3197542482df22c2a131d4a813280bd7c54cedf5
Version: 3197542482df22c2a131d4a813280bd7c54cedf5
Version: 3197542482df22c2a131d4a813280bd7c54cedf5
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\naudit: Fix data races of skb_queue_len() readers on audit_queue\n\nMultiple readers access audit_queue.qlen via skb_queue_len() without\nholding the queue lock or using READ_ONCE(), while kauditd writes to\nthis field via the skb_dequeue() \u2192 __skb_unlink() path with WRITE_ONCE()\nprotected by a spinlock. This constitutes data races.\n\nAll affected skb_queue_len(\u0026audit_queue) call sites:\n  - kauditd_thread() wait_event_freezable() condition\n  - audit_receive_msg() AUDIT_GET handler (s.backlog assignment)\n  - audit_receive() backlog check\n  - audit_log_start() backlog check and pr_warn()\n\nKCSAN reports the following conflicting access pattern (one example):\n==================================================================\nBUG: KCSAN: data-race in audit_log_start / skb_dequeue\n\nwrite (marked) to 0xffffffff8512ee20 of 4 bytes by task 661 on cpu 57:\n skb_dequeue+0x70/0xf0\n kauditd_send_queue+0x71/0x220\n kauditd_thread+0x1cb/0x430\n kthread+0x1c2/0x210\n ret_from_fork+0x162/0x1a0\n ret_from_fork_asm+0x1a/0x30\n\nread to 0xffffffff8512ee20 of 4 bytes by task 36586 on cpu 1:\n audit_log_start+0x2a0/0x6b0\n audit_core_dumps+0x64/0xa0\n do_coredump+0x14b/0x1260\n get_signal+0xeb2/0xf70\n arch_do_signal_or_restart+0x41/0x170\n exit_to_user_mode_loop+0xa2/0x1c0\n do_syscall_64+0x1a3/0x1c0\n entry_SYSCALL_64_after_hwframe+0x76/0xe0\n\nvalue changed: 0x00000001 -\u003e 0x00000000\n==================================================================\n\nResolve the race by switching to lockless helper skb_queue_len_lockless(),\nwhich internally uses READ_ONCE() and properly pairs with the WRITE_ONCE()\nwrite accesses already present on the writer side.\n\n[PM: line length tweak]"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.2,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - Unauthenticated packets matching a pre-existing nftables audit-level logging or xtables AUDIT rule reach audit_log_start() through the network receive and netfilter paths.\nAC:L - Parallel matching traffic invokes the vulnerable readers while feeding and waking kauditd, allowing the attacker to repeatedly drive both sides of the race.\nPR:N - The audit rule must already be configured, but the remote attacker needs no credentials or capabilities to send matching packets.\nUI:N - No victim action is required after the affected network-audit configuration is active.\nS:U - The race and its effects remain within the host kernel and its audit security authority.\nC:N - The raced value is only the 32-bit queue length; no pointer, packet contents, or adjacent memory is disclosed.\nI:L - An incorrect backlog decision can delay or discard audit records, causing limited corruption of the security audit trail without an arbitrary-write primitive.\nA:H - In hardened systems using AUDIT_FAIL_PANIC, a raced queue length interpreted as exceeding the limit from the GFP_ATOMIC packet-audit path calls audit_log_lost() and can panic the kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:55:36.444Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/69f98fff30bdaa72b0cb0e7e078ab6456a0a59b0"
        },
        {
          "url": "https://git.kernel.org/stable/c/b35597bdae1a5d8395da4b9baa993b9b71f74d68"
        },
        {
          "url": "https://git.kernel.org/stable/c/e575dabb805252e3113fdc3f56f6ecacfde422d0"
        },
        {
          "url": "https://git.kernel.org/stable/c/7ff42312ccde549f8c698723822c7db35107a39b"
        },
        {
          "url": "https://git.kernel.org/stable/c/a3d85dec60bb0622360fc176b2a51abdbe2ff0ad"
        },
        {
          "url": "https://git.kernel.org/stable/c/fe997a84a385f840b593ead92e575503a5046cee"
        },
        {
          "url": "https://git.kernel.org/stable/c/c5186201fa7030289cc4fe23fae87a3fcb566856"
        },
        {
          "url": "https://git.kernel.org/stable/c/c9a71daaecb2fb1d8c704545cc0b1c920b9bf5d7"
        }
      ],
      "title": "audit: Fix data races of skb_queue_len() readers on audit_queue",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64435",
    "datePublished": "2026-07-25T08:51:09.688Z",
    "dateReserved": "2026-07-19T15:36:31.787Z",
    "dateUpdated": "2026-08-17T04:55:36.444Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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