CVE-2026-68284 (GCVE-0-2026-68284)
Vulnerability from cvelistv5
Published
2026-08-10 12:02
Modified
2026-08-19 16:32
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Fix cork use-after-free in tcp_bpf_sendmsg() tcp_bpf_sendmsg() keeps msg_tx across sk_stream_wait_memory(), which drops and reacquires the socket lock. Its error path tries to decide whether msg_tx names the local temporary message by comparing it with the current value of psock->cork. This comparison is unsafe when two threads send on the same socket: Thread A Thread B msg_tx = psock->cork sk_msg_alloc() fails sk_stream_wait_memory() releases the socket lock acquires the socket lock completes the cork psock->cork = NULL frees the cork reacquires the socket lock msg_tx != psock->cork sk_msg_free(msg_tx) The stale cork is therefore mistaken for the local temporary message and freed again. KASAN reported: BUG: KASAN: slab-use-after-free in sk_msg_free+0x49/0x50 Read of size 4 at addr ffff88810c908800 by task poc/90 Call Trace: sk_msg_free+0x49/0x50 tcp_bpf_sendmsg+0x14f5/0x1cc0 __sys_sendto+0x32c/0x3a0 __x64_sys_sendto+0xdb/0x1b0 Allocated by task 89: __kasan_kmalloc+0x8f/0xa0 tcp_bpf_sendmsg+0x16b3/0x1cc0 Freed by task 91: __kasan_slab_free+0x43/0x70 kfree+0x131/0x3c0 tcp_bpf_sendmsg+0xec3/0x1cc0 msg_tx can only name the stack-local tmp or the shared cork. Check for tmp directly so a changed psock->cork cannot turn a shared message into an apparent local one.
References
Impacted products
Vendor Product Version
Linux Linux Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
Version: 604326b41a6fb9b4a78b6179335decee0365cd8c
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/tcp_bpf.c"
          ],
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "version": "0",
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            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf, sockmap: Fix cork use-after-free in tcp_bpf_sendmsg()\n\ntcp_bpf_sendmsg() keeps msg_tx across sk_stream_wait_memory(), which\ndrops and reacquires the socket lock.  Its error path tries to decide\nwhether msg_tx names the local temporary message by comparing it with\nthe current value of psock-\u003ecork.\n\nThis comparison is unsafe when two threads send on the same socket:\n\n  Thread A                         Thread B\n  msg_tx = psock-\u003ecork\n  sk_msg_alloc() fails\n  sk_stream_wait_memory()\n    releases the socket lock      acquires the socket lock\n                                  completes the cork\n                                  psock-\u003ecork = NULL\n                                  frees the cork\n    reacquires the socket lock\n  msg_tx != psock-\u003ecork\n  sk_msg_free(msg_tx)\n\nThe stale cork is therefore mistaken for the local temporary message\nand freed again.  KASAN reported:\n\n  BUG: KASAN: slab-use-after-free in sk_msg_free+0x49/0x50\n  Read of size 4 at addr ffff88810c908800 by task poc/90\n  Call Trace:\n   sk_msg_free+0x49/0x50\n   tcp_bpf_sendmsg+0x14f5/0x1cc0\n   __sys_sendto+0x32c/0x3a0\n   __x64_sys_sendto+0xdb/0x1b0\n  Allocated by task 89:\n   __kasan_kmalloc+0x8f/0xa0\n   tcp_bpf_sendmsg+0x16b3/0x1cc0\n  Freed by task 91:\n   __kasan_slab_free+0x43/0x70\n   kfree+0x131/0x3c0\n   tcp_bpf_sendmsg+0xec3/0x1cc0\n\nmsg_tx can only name the stack-local tmp or the shared cork. Check for\ntmp directly so a changed psock-\u003ecork cannot turn a shared message into\nan apparent local one."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerability is triggered by local `sendmsg()`/`sendto()` syscalls issued concurrently by two threads on the same TCP socket attached to a BPF sockmap; the remote peer cannot drive the race, so this is a local attack surface.\nAC:L - The attacker controls both sides of the race: it owns both sending threads, can force the `wait_for_memory` path deterministically with a small SO_SNDBUF plus a large blocking send, and can force `sk_stream_wait_memory()` to fail via SO_SNDTIMEO or a socket error, making the stale-cork free reliably reachable.\nPR:L - Once the sockmap and sk_msg verdict/cork program are installed by the platform (a standard deployment such as Cilium/Istio sockops acceleration), an ordinary unprivileged local process owning a socket in the map triggers the bug with plain send syscalls; no capability check guards `tcp_bpf_sendmsg()` itself.\nUI:N - The attacker\u0027s own two threads perform all the required sends; no action by any other user or victim process is needed.\nS:U - The use-after-free corrupts kernel slab and page state within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - `sk_msg_free()` reads the freed `sk_msg` cork object (KASAN slab-use-after-free read), and by reclaiming that slab object with attacker-groomed data the freed scatterlist can be steered to leak or expose arbitrary kernel memory contents.\nI:H - Beyond the stale read, the path re-frees the cork\u0027s scatterlist pages and uncharges socket memory, giving a double-free/page-refcount-underflow primitive on an attacker-groomable slab object, which is classically leveraged into arbitrary kernel write and control-flow hijack.\nA:H - The use-after-free and duplicate page release corrupt slab and page allocator state, reliably producing a kernel oops or panic and taking the whole system down."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-19T16:32:41.174Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0688e6fe599d2d39147ae9ece97944c6e1815ebf"
        },
        {
          "url": "https://git.kernel.org/stable/c/b2bcbeabfd843d47468fa095b1bd08ddb90cf616"
        },
        {
          "url": "https://git.kernel.org/stable/c/54be47e7cbb936429c3bbdfc526ea943954aaf80"
        },
        {
          "url": "https://git.kernel.org/stable/c/ee762f684eefa59de34d9ed93cab08336e834f47"
        },
        {
          "url": "https://git.kernel.org/stable/c/cde4d6bcd9b73073c66498f6723c7b364c4dbc18"
        },
        {
          "url": "https://git.kernel.org/stable/c/786d690257ec7a0c839f8710456e444ce3f1348b"
        },
        {
          "url": "https://git.kernel.org/stable/c/752b1159ed5d0c48fe169a3721b96660a9822aa1"
        },
        {
          "url": "https://git.kernel.org/stable/c/2d66a033864e27ab8d5e44cb36f31d9d2413bee4"
        }
      ],
      "title": "bpf, sockmap: Fix cork use-after-free in tcp_bpf_sendmsg()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68284",
    "datePublished": "2026-08-10T12:02:16.572Z",
    "dateReserved": "2026-07-30T09:28:09.379Z",
    "dateUpdated": "2026-08-19T16:32:41.174Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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