GHSA-GWFV-775P-2RJ5
Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31In the Linux kernel, the following vulnerability has been resolved:
net/atm: fix slab-out-of-bounds read in vcc_setsockopt()
vcc_setsockopt() contained an ineffective optlen check: if (__SO_LEVEL_MATCH(optname, level) && optlen != __SO_SIZE(optname)) return -EINVAL;
If __SO_LEVEL_MATCH(optname, level) evaluated to false (e.g. if the caller passed a mismatched level), the length check optlen != __SO_SIZE(optname) was short-circuited and bypassed. Execution then fell through to switch(optname), calling copy_from_sockptr() assuming optval contained sufficient space.
Furthermore, even if level matched, a cgroup BPF setsockopt filter could shrink optlen after entry. Because copy_from_sockptr() on kernel pointers uses memcpy(), this leads to a KASAN slab-out-of-bounds read when optlen is smaller than the expected structure size.
Fix this by using copy_safe_from_sockptr(), which unconditionally validates that optlen is at least the expected size before copying. Also change the local 'value' variable type from 'unsigned long' to 'int' so that SO_SETCLP matches its sizeof(int) ABI encoding on 64-bit systems.
{
"affected": [],
"aliases": [
"CVE-2026-74689"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-22T16:16:43Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/atm: fix slab-out-of-bounds read in vcc_setsockopt()\n\nvcc_setsockopt() contained an ineffective optlen check:\n if (__SO_LEVEL_MATCH(optname, level) \u0026\u0026 optlen != __SO_SIZE(optname))\n return -EINVAL;\n\nIf __SO_LEVEL_MATCH(optname, level) evaluated to false (e.g. if the caller\npassed a mismatched level), the length check optlen != __SO_SIZE(optname)\nwas short-circuited and bypassed. Execution then fell through to switch(optname),\ncalling copy_from_sockptr() assuming optval contained sufficient space.\n\nFurthermore, even if level matched, a cgroup BPF setsockopt filter could shrink\noptlen after entry. Because copy_from_sockptr() on kernel pointers uses memcpy(),\nthis leads to a KASAN slab-out-of-bounds read when optlen is smaller than the\nexpected structure size.\n\nFix this by using copy_safe_from_sockptr(), which unconditionally validates\nthat optlen is at least the expected size before copying. Also change the local\n\u0027value\u0027 variable type from \u0027unsigned long\u0027 to \u0027int\u0027 so that SO_SETCLP matches\nits sizeof(int) ABI encoding on 64-bit systems.",
"id": "GHSA-gwfv-775p-2rj5",
"modified": "2026-08-25T06:31:27Z",
"published": "2026-08-22T18:30:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74689"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2c5988c7349c0b64a7e0441bfc6e1dca54f7116a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/35f258fee9ed358c6d0f57f91c30bf029c3724af"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6eb6af88710977eb529b558a07294874d8c40c4d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9f77c1ab382188f5b51982fab6d913443b6dc59f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b3bcd5d65ac03c15787b2a5b36c718e26a689336"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d0c80dbb970439bd2eeb0e5effff8c16a5f4e1e3"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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