---
id: CVE-2026-15534
title: >-
  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…
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…
severity: medium
cvss: 5.7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H'
cwe:
  - CWE-125
  - CWE-190
  - CWE-787
product: perl
affected:
  - perl <= 5.45.1
published: '2026-08-09'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T22:17:38.113'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-15534'
references:
  - url: >-
      https://github.com/Perl/perl5/commit/54cf3d44cbbedd17d774e9a37921963e8fd5d0cb.patch
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: >-
      https://github.com/Perl/perl5/commit/568e6fd238867bb9e99fa3f47cba3169009239e0.patch
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: 'http://www.openwall.com/lists/oss-security/2026/08/09/12'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2026/08/09/13'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-15534.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-15534'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2512950'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-15534'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-15534'
  - url: 'https://access.redhat.com/errata/RHSA-2026:63403'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-08-12T17:38:23.129391Z'
epss: 0.00256
epssPercentile: 0.15342
ingestedAt: '2026-08-10T03:38:50.657Z'
vendor: Red Hat
patched:
  - hardened_images
---

## Overview

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.

## Remediation

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

## Vendor advisories

- **RHSA-2026:63403** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:63403)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift AI (RHOAI), … · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, … · updated 2026-09-08 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-15534.json)