# CVE-2026-74371

## Summary

- **CVE ID:** CVE-2026-74371
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Aug 15, 2026
- **Last Modified:** Sep 14, 2026

## Description

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 Products

- Linux — Linux (1209339844601ec1766f4ff430673fbcfe42bb51)
- Linux — Linux (6.17)
- Linux — Linux (0)
- Linux — Linux (6.18.40)
- Linux — Linux (7.1.5)
- Linux — Linux (7.2-rc1)
- Linux — Linux (7.2)
- Linux — Linux (195814a38a6a712bcb44d3dfa5109e926e92bec4)

## References

- [CNA](https://git.kernel.org/stable/c/a7131340d0f95df9a541257dccab5d85e6bcdd2b)
- [CNA](https://git.kernel.org/stable/c/d3d630e8a7f3421bc2d204b87bdff35b4432a8e3)
- [CNA](https://git.kernel.org/stable/c/21c4b99b27f3f85b89256e81b3e997dec0a460d0)
- [CNA](https://git.kernel.org/stable/c/b78eb6efbf052d44a3a14726aa7c7d5aa2e544d7)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.13%
- **EPSS Percentile:** 2.9

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-19._