---
id: CVE-2026-74371
title: 'bpf: fix BPF_PROG_QUERY OOB write and cgroup backward compat'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: fix BPF_PROG_QUERY OOB write and cgroup backward compat

  BPF_PROG_QUERY writes back the 'query.revision' field unconditionally to
  userspace. If userspace passes a …
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 195814a38a6a712bcb44d3dfa5109e926e92bec4 <
    b78eb6efbf052d44a3a14726aa7c7d5aa2e544d7
  - >-
    Linux >= 1209339844601ec1766f4ff430673fbcfe42bb51 <
    a7131340d0f95df9a541257dccab5d85e6bcdd2b
  - >-
    Linux >= 1209339844601ec1766f4ff430673fbcfe42bb51 <
    d3d630e8a7f3421bc2d204b87bdff35b4432a8e3
  - >-
    Linux >= 1209339844601ec1766f4ff430673fbcfe42bb51 <
    21c4b99b27f3f85b89256e81b3e997dec0a460d0
  - Linux 6.17
published: '2026-08-15'
updated: '2026-09-14'
sourceUpdated: '2026-09-14T11:58:45.047Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-74371'
references:
  - url: 'https://git.kernel.org/stable/c/b78eb6efbf052d44a3a14726aa7c7d5aa2e544d7'
  - url: 'https://git.kernel.org/stable/c/a7131340d0f95df9a541257dccab5d85e6bcdd2b'
  - url: 'https://git.kernel.org/stable/c/d3d630e8a7f3421bc2d204b87bdff35b4432a8e3'
  - url: 'https://git.kernel.org/stable/c/21c4b99b27f3f85b89256e81b3e997dec0a460d0'
tags:
  - cve.org
epss: 0.00175
epssPercentile: 0.06143
ingestedAt: '2026-09-14T15:23:07.456Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

bpf: fix BPF_PROG_QUERY OOB write and cgroup backward compat

BPF_PROG_QUERY writes back the 'query.revision' field unconditionally to
userspace. If userspace passes a smaller 'bpf_attr' structure (e.g. 40
bytes, which was the layout before the addition of 'query.revision'),
the kernel performs an out-of-bounds write.

Fix this by propagating the user-provided attribute size 'uattr_size'
down to the cgroup query handlers, and conditionally skipping writing
the revision field to userspace when the provided buffer size is
insufficient.

query.revision in bpf_mprog_query is structurally identical to the
cgroup case: a late tail field, written unconditionally.

But the backward-compat hazard is not the same.

The min-historical-size test is per command, and bpf_mprog_query only
serves attach types that were born with revision in the struct:

- tcx_prog_query -> BPF_TCX_INGRESS/EGRESS
- netkit_prog_query -> BPF_NETKIT_PRIMARY/PEER

tcx, netkit, the revision field, and bpf_mprog_query itself all landed in
the same v6.6 merge window (053c8e1f235d added the mprog query API +
revision; tcx in e420bed02507, netkit in 35dfaad7188c). There has never
been a tcx/netkit BPF_PROG_QUERY userspace that doesn't know about
revision. So for these commands the minimum legitimate struct already
covers offset 56-64 — no old binary can be broken here.

Contrast with cgroup: BPF_PROG_QUERY on cgroup attach types shipped in
2017; revision write-back was bolted on years later (120933984460). That
path has a real population of pre-revision callers.

## Affected

- `Linux >= 195814a38a6a712bcb44d3dfa5109e926e92bec4 < b78eb6efbf052d44a3a14726aa7c7d5aa2e544d7`
- `Linux >= 1209339844601ec1766f4ff430673fbcfe42bb51 < a7131340d0f95df9a541257dccab5d85e6bcdd2b`
- `Linux >= 1209339844601ec1766f4ff430673fbcfe42bb51 < d3d630e8a7f3421bc2d204b87bdff35b4432a8e3`
- `Linux >= 1209339844601ec1766f4ff430673fbcfe42bb51 < 21c4b99b27f3f85b89256e81b3e997dec0a460d0`
- `Linux 6.17`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.