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Fencer Vulns
medium 5.7

CVE-2026-15534 json

Perl versions through 5.45.1 have out-of-bounds heap reads and writes during regular expression matching via an undersized superlinear cache in S_regmatch

published 2026-08-09 3 mo ago modified 2026-10-23 16 d ago also EUVD-2026-54935

cvss
5.7
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 5%
public exploits
0
none known

Summary

Perl versions through 5.45.1 have out-of-bounds heap reads and writes during regular expression matching via an undersized superlinear cache in S_regmatch.

The regex engine's superlinear cache holds one bit per subject position for each participating WHILEM node, so the bit count is the subject length plus one times the number of nodes. Nothing checks that product for positive overflow of the signed 32-bit count: a 286331153 byte subject matched against a pattern with 15 participating nodes stores the count as 14, leaving a two byte cache. The cache is then indexed from the real match position and node number, so reads go past the end of the allocation, and on failure CACHEsayNO sets a bit past it.

A caller that matches an attacker controlled subject of this size against a pattern of this shape can crash the process or corrupt heap memory.

Patch / fix

  • perl Ubuntu 22.04 LTS 5.34.0-3ubuntu1.9
  • perl Ubuntu 24.04 LTS 5.38.2-3.2ubuntu0.6
  • perl Ubuntu 26.04 LTS 5.40.1-7ubuntu0.2
  • perl Ubuntu Pro 14.04 LTS 5.18.2-2ubuntu1.7+esm9
  • perl Ubuntu Pro 16.04 LTS 5.22.1-9ubuntu0.9+esm4
  • perl Ubuntu Pro 18.04 LTS 5.26.1-6ubuntu0.7+esm4
  • perl Ubuntu Pro 20.04 LTS 5.30.0-9ubuntu0.5+esm4

ubuntu advisories UBUNTU-CVE-2026-15534

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 hummingbird 1 5.42.2-525.1.hum1
  • perl-B hummingbird 1 1.89-525.1.hum1
  • perl-if hummingbird 1 0.61.000-525.1.hum1
  • perl-IO hummingbird 1 1.55-525.1.hum1
  • perl-ph hummingbird 1 5.42.2-525.1.hum1
  • perl-lib hummingbird 1 0.65-525.1.hum1
  • perl-mro hummingbird 1 1.29-525.1.hum1
  • perl-Net hummingbird 1 1.04-525.1.hum1

red hat advisories RHSA-2026:63403

  • perl Azure Linux 3.0 5.38.2-516

azure linux advisories AZL-94670

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-2026-15534 updated cvss 5.7

perl: Perl: Arbitrary code execution via out-of-bounds memory access in regular expression engine.

  • Red Hat Enterprise Linux 6 perl, perl-CGI, perl-core, perl-CPAN, perl-libs, perl-parent, +39 more Red Hat Enterprise Linux 7 perl, perl-core, perl-CPAN, perl-libs, perl-tests, perl-macros, +11 more Red Hat Enterprise Linux 8 perl, perl-IO, perl-libs, perl-open, perl-Test, perl-Errno, +19 more Red Hat Enterprise Linux 9 perl, perl-B, perl-if, perl-IO, perl-ph, perl-lib, +92 more Red Hat Enterprise Linux 10 perl Red Hat OpenShift AI (RHOAI) rhoai/odh-workbench-codeserver-datascience-cpu-py312-rhel9
    +3 more products
    Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9 Red Hat OpenShift Dev Spaces devspaces/code-rhel9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images perl 5.42.2-525.1.hum1, perl-B 1.89-525.1.hum1, perl-IO 1.55-525.1.hum1, perl-Tie 4.6-525.1.hum1, perl-lib 0.65-525.1.hum1, perl-mro 1.29-525.1.hum1, +93 more
    fixed: vendor fix RHSA-2026:63403

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
2 mo ago

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 5.7 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
CNA 3.1 5.7 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

Classification

Weakness

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.