GHSA-6PXH-C54R-CXC3
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix effective prog array index with BPF_F_PREORDER
replace_effective_prog() and purge_effective_progs() located the slot in the effective array by walking the program hlist and counting entries linearly. That count does not match the array layout: compute_effective_ progs() places BPF_F_PREORDER programs at the front (ancestor cgroup first, attach order within a cgroup) and the rest after them (descendant cgroup first). So when a preorder program is present, the linear hlist position no longer equals the program's index in the effective array.
For replace_effective_prog() (bpf_link_update()) this overwrote the wrong slot, corrupting the effective order. For purge_effective_progs(), it could dummy out a slot belonging to a different program and leave the detached program in the array while bpf_prog_put() drops its reference, i.e. a use-after-free.
Fix both by replaying compute_effective_progs()'s placement (including the per-cgroup preorder reversal) in a shared effective_prog_pos() helper. Identify the entry by its struct bpf_prog_list pointer rather than by (prog, link) value, so the lookup resolves to exactly the attachment the syscall selected even when the same bpf_prog is attached to several cgroups in the hierarchy.
{
"affected": [],
"aliases": [
"CVE-2026-72427"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:16Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix effective prog array index with BPF_F_PREORDER\n\nreplace_effective_prog() and purge_effective_progs() located the slot in\nthe effective array by walking the program hlist and counting entries\nlinearly. That count does not match the array layout: compute_effective_\nprogs() places BPF_F_PREORDER programs at the front (ancestor cgroup\nfirst, attach order within a cgroup) and the rest after them (descendant\ncgroup first). So when a preorder program is present, the linear hlist\nposition no longer equals the program\u0027s index in the effective array.\n\nFor replace_effective_prog() (bpf_link_update()) this overwrote the\nwrong slot, corrupting the effective order. For purge_effective_progs(),\nit could dummy out a slot belonging to a different program and leave the\ndetached program in the array while bpf_prog_put() drops its reference,\ni.e. a use-after-free.\n\nFix both by replaying compute_effective_progs()\u0027s placement (including\nthe per-cgroup preorder reversal) in a shared effective_prog_pos()\nhelper. Identify the entry by its struct bpf_prog_list pointer rather\nthan by (prog, link) value, so the lookup resolves to exactly the\nattachment the syscall selected even when the same bpf_prog is attached\nto several cgroups in the hierarchy.",
"id": "GHSA-6pxh-c54r-cxc3",
"modified": "2026-08-17T06:33:29Z",
"published": "2026-08-15T06:32:24Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72427"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/41b4320b84fdafe1ab586b06453d30d50415db59"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/525e408c27ae714e538b8c608c3a974df3ab6c92"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9697db03e010391c55ae75192cbdf30c5a72c114"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b584f107ab90222bd825dcb4c5977326ff684109"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f08aaee3152d0dfc578b3f2586932d82062701dd"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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