---
id: CVE-2026-89761
title: 'apparmor: fix out-of-bounds write when null terminating a label vec'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  apparmor: fix out-of-bounds write when null terminating a label vec

  aa_vec_unique() null terminates at vec[n - dups] when VEC_FLAG_TERMINATE
  is passed. If the componen…
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
cwe:
  - CWE-787
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 <
    b17c8f5dcb36a032688847b2bce4bd813b4baad1
  - >-
    Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 <
    9124e078ea2250d8d01d2162a550acb01ef5bf48
  - >-
    Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 <
    28069434aef66b9d084f0609b7a29c171846815e
  - >-
    Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 <
    36bdd0b45ec3f4822832a56e9db8674c8450dfce
  - >-
    Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 <
    9f1e40193eef7f047e6b77cfb4b4cafdecd7a123
  - Linux 4.13
published: '2026-09-11'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:48:38.023Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89761'
references:
  - url: 'https://git.kernel.org/stable/c/b17c8f5dcb36a032688847b2bce4bd813b4baad1'
  - url: 'https://git.kernel.org/stable/c/9124e078ea2250d8d01d2162a550acb01ef5bf48'
  - url: 'https://git.kernel.org/stable/c/28069434aef66b9d084f0609b7a29c171846815e'
  - url: 'https://git.kernel.org/stable/c/36bdd0b45ec3f4822832a56e9db8674c8450dfce'
  - url: 'https://git.kernel.org/stable/c/9f1e40193eef7f047e6b77cfb4b4cafdecd7a123'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89761.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89761'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532235'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89761'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89761'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89761.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.0012
epssPercentile: 0.01832
scores:
  cna: 7.8
  vendor: 5.5
ingestedAt: '2026-09-14T15:23:07.472Z'
---

## Overview

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

apparmor: fix out-of-bounds write when null terminating a label vec

aa_vec_unique() null terminates at vec[n - dups] when VEC_FLAG_TERMINATE
is passed. If the components are all distinct no duplicates are dropped,
dups is 0 and the terminator goes to vec[n], so the caller has to provide
room for n + 1 entries.

aa_label_strn_parse() sets up its vector with vec_setup(profile, vec, len,
gfp) and then calls aa_vec_unique(vec, len, VEC_FLAG_TERMINATE), but
vec_setup() does not reserve the terminator entry. Up to LOCAL_VEC_ENTRIES
it uses the local array of LOCAL_VEC_ENTRIES pointers, above that it
allocates exactly len pointers. The terminator therefore lands one entry
past the end of the local array when len is LOCAL_VEC_ENTRIES, and one
entry past the end of the allocation when len is larger.

len comes from the number of "//&" separated components in the label name
and label_count_strn_entries() does not bound it. An unprivileged task
reaches the parse by writing to /proc/self/attr/apparmor/current or through
lsm_set_self_attr(2), both of which go through do_setattr(), and the name
is parsed before the change_profile permission is checked.
The query_label() path behind the securityfs .access file, which is
mode 0666, performs no permission check at all. Every component has to
resolve to a loaded profile, so a system with policy loaded is required.

The other two VEC_FLAG_TERMINATE users work on a label vec that
aa_label_alloc() has already sized with "+ 1 for null terminator entry on
vec". Reserve the same entry in vec_setup() and DEFINE_VEC(). Passing
len + 1 from the caller instead would move len == LOCAL_VEC_ENTRIES out of
the local array and into kzalloc().

## Affected

- `Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < b17c8f5dcb36a032688847b2bce4bd813b4baad1`
- `Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 9124e078ea2250d8d01d2162a550acb01ef5bf48`
- `Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 28069434aef66b9d084f0609b7a29c171846815e`
- `Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 36bdd0b45ec3f4822832a56e9db8674c8450dfce`
- `Linux >= f1bd904175e8190ce14aedee37e207ab51fe3b30 < 9f1e40193eef7f047e6b77cfb4b4cafdecd7a123`
- `Linux 4.13`

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89761.json)