Skip to content
Fencer Vulns
critical 9.1

CVE-2025-40908 json

YAML-LibYAML prior to 0.903.0 for Perl uses 2-args open, allowing existing files to be modified

published 2025-06-01 17 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-16577

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

YAML-LibYAML prior to 0.903.0 for Perl uses 2-args open, allowing existing files to be modified

Patch / fix

  • TINITA YAML::LibYAML 0.903.0
  • libyaml-libyaml-perl Debian 12 0.86+ds-1+deb12u1
  • libyaml-libyaml-perl Debian 14, Debian 13 0.903.0+ds-1

debian advisories DEBIAN-CVE-2025-40908

  • libyaml-libyaml-perl Ubuntu 22.04 LTS 0.83+ds-1ubuntu0.22.04.1
  • libyaml-libyaml-perl Ubuntu 24.04 LTS 0.89+ds-1ubuntu0.24.04.1

ubuntu advisories UBUNTU-CVE-2025-40908

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • perl-YAML-LibYAML RHEL 9 1:0.82-6.1.el9_6
  • perl-YAML-LibYAML RHEL 8 1:0.70-2.el8_10
  • perl-YAML-LibYAML RHEL 9.4 EUS 1:0.82-6.el9_4.1

red hat advisories RHSA-2025:9338RHSA-2025:9330RHSA-2025:9329

  • perl-YAML-LibYAML SLE Module for Development Tools 15 SP7, SLE Module for Development Tools 15 SP6, openSUSE Leap 15.6 0.904.0-150000.3.16.1
  • perl-YAML-LibYAML SLE Module for Development Tools 15 SP6, openSUSE Leap 15.6 0.890.0-150000.3.11.1
  • perl-YAML-LibYAML SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 0.38-11.3.1

suse advisories SUSE-RU-2025:03081-1SUSE-SU-2025:01885-2SUSE-SU-2025:01886-1SUSE-SU-2025:01885-1

  • perl-YAML-LibYAML openSUSE Tumbleweed 0.904.0-2.1

opensuse advisories openSUSE-SU-2025:15261-1

  • perl-YAML-LibYAML AlmaLinux 8 1:0.70-2.el8_10
  • perl-YAML-LibYAML AlmaLinux 9 1:0.82-6.1.el9_6

almalinux advisories ALSA-2025:9329ALSA-2025:9330

  • perl-YAML-LibYAML Rocky Linux 9 1:0.82-6.1.el9_6
  • perl-YAML-LibYAML Rocky Linux 8 1:0.70-2.el8_10

rocky linux advisories RLSA-2025:9330RLSA-2025:9329

  • perl-YAML-LibYAML Azure Linux 3.0 0.902.0-2

azure linux advisories AZL-62242

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2025-40908 updated cvss 7.7

yaml-libyaml: LibYAML Perl File Modification Vulnerability

  • Red Hat CodeReady Linux Builder EUS (v.9.4) perl-YAML-LibYAML 0.82-6.el9_4.1
    fixed: vendor fix RHSA-2025:9338
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) perl-YAML-LibYAML 0.82-6.1.el9_6
    fixed: vendor fix RHSA-2025:9330
  • Red Hat Enterprise Linux CRB (v. 8) perl-YAML-LibYAML 0.70-2.el8_10
    fixed: vendor fix RHSA-2025:9329

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
yes
Technical impact
total
Assessed
17 mo ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/ingydotnet/yaml-libyaml-pm/issues/120 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

  • TINITA YAML::LibYAML

Classification

Weakness
  • CWE-552 Files or Directories Accessible to External Parties

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.