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Fencer Vulns
high 7.1

CVE-2025-39840 json

audit: fix out-of-bounds read in audit_compare_dname_path()

published 2025-09-19 13 mo ago modified 2026-10-19 20 d ago also EUVD-2025-30360

cvss
7.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

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

audit: fix out-of-bounds read in audit_compare_dname_path()

When a watch on dir=/ is combined with an fsnotify event for a single-character name directly under / (e.g., creating /a), an out-of-bounds read can occur in audit_compare_dname_path().

The helper parent_len() returns 1 for "/". In audit_compare_dname_path(), when parentlen equals the full path length (1), the code sets p = path + 1 and pathlen = 1 - 1 = 0. The subsequent loop then dereferences p[pathlen - 1] (i.e., p[-1]), causing an out-of-bounds read.

Fix this by adding a pathlen > 0 check to the while loop condition to prevent the out-of-bounds access.

[PM: subject tweak, sign-off email fixes]

Patch / fix

  • Linux Linux 6.16.6, 6.17
  • linux Debian 14 6.16.6-1

debian advisories DEBIAN-CVE-2025-39840

  • kernel RHEL 10.1 6.12.0-124.27.1.el10_1
  • rv RHEL 10.1 6.12.0-124.27.1.el10_1
  • perf RHEL 10.1 6.12.0-124.27.1.el10_1
  • rtla RHEL 10.1 6.12.0-124.27.1.el10_1
  • libperf RHEL 10.1 6.12.0-124.27.1.el10_1
  • kernel-rt RHEL 10.1 6.12.0-124.27.1.el10_1
  • kernel-64k RHEL 10.1 6.12.0-124.27.1.el10_1
  • kernel-core RHEL 10.1 6.12.0-124.27.1.el10_1

red hat advisories RHSA-2026:0453RHSA-2026:0445

  • kernel AlmaLinux 9 5.14.0-611.20.1.el9_7
  • rv AlmaLinux 9 5.14.0-611.20.1.el9_7
  • perf AlmaLinux 9 5.14.0-611.20.1.el9_7
  • rtla AlmaLinux 9 5.14.0-611.20.1.el9_7
  • libperf AlmaLinux 9 5.14.0-611.20.1.el9_7
  • kernel-rt AlmaLinux 9 5.14.0-611.20.1.el9_7
  • kernel-64k AlmaLinux 9 5.14.0-611.20.1.el9_7
  • kernel-core AlmaLinux 9 5.14.0-611.20.1.el9_7

almalinux advisories ALSA-2026:0445ALSA-2026:0453

  • kernel Rocky Linux 10 6.12.0-124.27.1.el10_1
  • kernel Rocky Linux 9 5.14.0-611.20.1.el9_7

rocky linux advisories RLSA-2026:0453RLSA-2026:0445

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-39840 updated cvss 7.0

kernel: audit: fix out-of-bounds read in audit_compare_dname_path()

  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-611.20.1.el9_7, perf 5.14.0-611.20.1.el9_7, rtla 5.14.0-611.20.1.el9_7, python3-perf 5.14.0-611.20.1.el9_7, kernel-devel-matched 5.14.0-611.20.1.el9_7, kernel-64k-devel-matched 5.14.0-611.20.1.el9_7, +7 more
    fixed: vendor fix RHSA-2026:0445
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-124.27.1.el10_1, perf 6.12.0-124.27.1.el10_1, rtla 6.12.0-124.27.1.el10_1, python3-perf 6.12.0-124.27.1.el10_1, kernel-devel-matched 6.12.0-124.27.1.el10_1, kernel-64k-devel-matched 6.12.0-124.27.1.el10_1, +7 more
    fixed: vendor fix RHSA-2026:0453
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-611.20.1.el9_7, kernel-64k 5.14.0-611.20.1.el9_7, kernel-core 5.14.0-611.20.1.el9_7, kernel-tools 5.14.0-611.20.1.el9_7, kernel-modules 5.14.0-611.20.1.el9_7, kernel-64k-core 5.14.0-611.20.1.el9_7, +27 more
    fixed: vendor fix RHSA-2026:0445
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-124.27.1.el10_1, kernel-64k 6.12.0-124.27.1.el10_1, kernel-core 6.12.0-124.27.1.el10_1, kernel-tools 6.12.0-124.27.1.el10_1, kernel-modules 6.12.0-124.27.1.el10_1, kernel-64k-core 6.12.0-124.27.1.el10_1, +28 more
    fixed: vendor fix RHSA-2026:0453
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-611.20.1.el9_7, kernel-debuginfo-common-s390x 5.14.0-611.20.1.el9_7, kernel-debuginfo-common-x86_64 5.14.0-611.20.1.el9_7, kernel-debuginfo-common-aarch64 5.14.0-611.20.1.el9_7, kernel-debuginfo-common-ppc64le 5.14.0-611.20.1.el9_7
    fixed: vendor fix RHSA-2026:0445
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-124.27.1.el10_1, kernel-debuginfo-common-s390x 6.12.0-124.27.1.el10_1, kernel-debuginfo-common-x86_64 6.12.0-124.27.1.el10_1, kernel-debuginfo-common-aarch64 6.12.0-124.27.1.el10_1, kernel-debuginfo-common-ppc64le 6.12.0-124.27.1.el10_1
    fixed: vendor fix RHSA-2026:0453
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-611.20.1.el9_7, kernel-rt-64k 5.14.0-611.20.1.el9_7, kernel-rt-core 5.14.0-611.20.1.el9_7, kernel-rt-modules 5.14.0-611.20.1.el9_7, kernel-rt-64k-core 5.14.0-611.20.1.el9_7, kernel-rt-debug-core 5.14.0-611.20.1.el9_7, +14 more
    fixed: vendor fix RHSA-2026:0445
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-124.27.1.el10_1, kernel-rt-64k 6.12.0-124.27.1.el10_1, kernel-rt-core 6.12.0-124.27.1.el10_1, kernel-rt-modules 6.12.0-124.27.1.el10_1, kernel-rt-64k-core 6.12.0-124.27.1.el10_1, kernel-rt-debug-core 6.12.0-124.27.1.el10_1, +14 more
    fixed: vendor fix RHSA-2026:0453
show 3 more
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-611.20.1.el9_7, kernel-rt-core 5.14.0-611.20.1.el9_7, kernel-rt-modules 5.14.0-611.20.1.el9_7, kernel-rt-debug-core 5.14.0-611.20.1.el9_7, kernel-rt-modules-core 5.14.0-611.20.1.el9_7, kernel-rt-debug-modules 5.14.0-611.20.1.el9_7, +4 more
    fixed: vendor fix RHSA-2026:0445
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-124.27.1.el10_1, kernel-rt-core 6.12.0-124.27.1.el10_1, kernel-rt-modules 6.12.0-124.27.1.el10_1, kernel-rt-debug-core 6.12.0-124.27.1.el10_1, kernel-rt-modules-core 6.12.0-124.27.1.el10_1, kernel-rt-debug-modules 6.12.0-124.27.1.el10_1, +4 more
    fixed: vendor fix RHSA-2026:0453
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
9 mo ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
CISA ADP 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
NVD 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.