GHSA-CQ66-2F6W-RHG5
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 12:31In the Linux kernel, the following vulnerability has been resolved:
af_unix: Update last skb marker in manage_oob().
Fahad Alharbi reported that blocking recv(MSG_PEEK) could hog CPU due to OOB skb.
In the following cases, manage_oob() skips OOB skb(s) and returns NULL for the last recv(MSG_PEEK):
socketpair(AF_UNIX, SOCK_STREAM, 0, sk);
1) skb -> OOB skb -> NULL send(sk[0], "ab", 2, MSG_OOB); recv(sk[1], buf, 0, MSG_PEEK);
2) skb -> consumed OOB skb -> NULL send(sk[0], "ab", 2, MSG_OOB); recv(sk[1], buf, 1, MSG_OOB); recv(sk[1], buf, 0, MSG_PEEK);
3) consumed OOB skb -> OOB skb -> NULL send(sk[0], "a", 1, MSG_OOB); recv(sk[1], buf, 0, MSG_OOB); send(sk[0], "b", 1, MSG_OOB); recv(sk[1], buf, 1, MSG_PEEK);
Then, @copied is 0 in unix_stream_read_generic() (zero-length buffer, or non-OOB skb is not yet consumed), and unix_stream_data_wait() is called.
However, it returns immediately because @last is not updated in unix_stream_read_generic(), and the thread busy-waits for a new skb.
Let's update @last in manage_oob().
For MSG_PEEK, @last is updated with the skipped OOB, and for the non-peek case, @last matches the returned value (when !copied) because OOB is unlinked.
Note that manage_oob() is inlined and no stack canary is added.
{
"affected": [],
"aliases": [
"CVE-2026-97985"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:26Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\naf_unix: Update last skb marker in manage_oob().\n\nFahad Alharbi reported that blocking recv(MSG_PEEK) could hog CPU\ndue to OOB skb.\n\nIn the following cases, manage_oob() skips OOB skb(s) and returns\nNULL for the last recv(MSG_PEEK):\n\n socketpair(AF_UNIX, SOCK_STREAM, 0, sk);\n\n 1) skb -\u003e OOB skb -\u003e NULL\n send(sk[0], \"ab\", 2, MSG_OOB);\n recv(sk[1], buf, 0, MSG_PEEK);\n\n 2) skb -\u003e consumed OOB skb -\u003e NULL\n send(sk[0], \"ab\", 2, MSG_OOB);\n recv(sk[1], buf, 1, MSG_OOB);\n recv(sk[1], buf, 0, MSG_PEEK);\n\n 3) consumed OOB skb -\u003e OOB skb -\u003e NULL\n send(sk[0], \"a\", 1, MSG_OOB);\n recv(sk[1], buf, 0, MSG_OOB);\n send(sk[0], \"b\", 1, MSG_OOB);\n recv(sk[1], buf, 1, MSG_PEEK);\n\nThen, @copied is 0 in unix_stream_read_generic() (zero-length buffer,\nor non-OOB skb is not yet consumed), and unix_stream_data_wait() is\ncalled.\n\nHowever, it returns immediately because @last is not updated in\nunix_stream_read_generic(), and the thread busy-waits for a new skb.\n\nLet\u0027s update @last in manage_oob().\n\nFor MSG_PEEK, @last is updated with the skipped OOB, and for the\nnon-peek case, @last matches the returned value (when !copied)\nbecause OOB is unlinked.\n\nNote that manage_oob() is inlined and no stack canary is added.",
"id": "GHSA-cq66-2f6w-rhg5",
"modified": "2026-09-25T12:31:31Z",
"published": "2026-09-25T12:31:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97985"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0630bfc773d85ac44da05b2c5a037dbbd39301ab"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/94fd4debd2e3a69cf93e766c8b328a810c228119"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f1816b3d7ce80dcf086bb68ff5ae6e09520ca1fa"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fc62a26493a98a0424d9dae2eb92a1daa1321f65"
}
],
"schema_version": "1.4.0",
"severity": []
}
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