---
id: CVE-2026-72111
title: 'bpf: Reset register bounds before narrowing retval range in check_mem_access()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Reset register bounds before narrowing retval range in check_mem_access()

  When the BPF verifier processes a context load of an LSM hook return
  value, it calls __m…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 <
    bde92f65042ec14389782dd223f706bf6b59ce5d
  - >-
    Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 <
    0993dc5fc619c0b25ab1310cb11d65e78351c0fe
  - >-
    Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 <
    5a55f9aecc08990940e70f0c7048a80850c5a16a
  - >-
    Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 <
    5e0b273e0a62cc04ec338c7b502797c66c2ed42a
  - Linux 1050727d83e70449991c29dd1cf29fe936a63da3
  - Linux 27ca3e20fe80be85a92b10064dfeb56cb2564b1c
  - Linux >= 6.10.13 < 6.11
  - Linux >= 6.11.2 < 6.12
  - Linux 6.12
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T18:41:38.213605Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:44:56.296Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72111'
references:
  - url: 'https://git.kernel.org/stable/c/bde92f65042ec14389782dd223f706bf6b59ce5d'
  - url: 'https://git.kernel.org/stable/c/0993dc5fc619c0b25ab1310cb11d65e78351c0fe'
  - url: 'https://git.kernel.org/stable/c/5a55f9aecc08990940e70f0c7048a80850c5a16a'
  - url: 'https://git.kernel.org/stable/c/5e0b273e0a62cc04ec338c7b502797c66c2ed42a'
tags:
  - cve.org
epss: 0.00176
epssPercentile: 0.06698
ingestedAt: '2026-10-16T19:46:24.432Z'
---

## Overview

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

bpf: Reset register bounds before narrowing retval range in check_mem_access()

When the BPF verifier processes a context load of an LSM hook return
value, it calls __mark_reg_s32_range() to narrow the register to the
hook's valid range. However, __mark_reg_s32_range() intersects the new
range with the register's existing bounds using max_t()/min_t() rather
than replacing them.

If the destination register carries stale bounds from a prior instruction
(e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than
reality. The verifier then believes it knows the register's exact value,
while at runtime the actual hook return value is loaded, creating a
verifier/runtime mismatch that can be used to bypass BPF memory safety
checks.

The else branch already calls mark_reg_unknown() to reset register state
before any narrowing. Apply the same reset in the is_retval path so
stale bounds are cleared before __mark_reg_s32_range() intersects.

## Affected

- `Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 < bde92f65042ec14389782dd223f706bf6b59ce5d`
- `Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 < 0993dc5fc619c0b25ab1310cb11d65e78351c0fe`
- `Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 < 5a55f9aecc08990940e70f0c7048a80850c5a16a`
- `Linux >= 5d99e198be279045e6ecefe220f5c52f8ce9bfd5 < 5e0b273e0a62cc04ec338c7b502797c66c2ed42a`
- `Linux 1050727d83e70449991c29dd1cf29fe936a63da3`
- `Linux 27ca3e20fe80be85a92b10064dfeb56cb2564b1c`
- `Linux >= 6.10.13 < 6.11`
- `Linux >= 6.11.2 < 6.12`
- `Linux 6.12`

## Remediation

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