CVE-2026-15534: 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

mediumCVSS 5.7CVE-2026-15534

CSIRTS triage

vendor: Perl product: Perl Memory corruptionaffected: through 5.45.1

What: Out-of-bounds heap reads and writes occur during regular expression matching due to an undersized superlinear cache in S_regmatch.
Who is affected: All systems running Perl versions up to and including 5.45.1.
Urgency: Medium priority; memory corruption in regex processing requires prompt patching.
Action: Upgrade to Perl 5.45.2 or later once available.

AI-assisted analysis generated from the source advisory — verify against the original.

⚡ Watch Perl

Get an email when a new Perl advisory drops — max one per day, one-click unsubscribe.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.7
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-15534

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-155340.16% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 6% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-15534	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Perl

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownCVE-2026-78655: Punk::Plugin::TOTP versions before 0.05 for Perl allow the second-factor attempt limit to be r…nvd · 2026-08-25
unknownCVE-2026-78619: Punk::Plugin::TOTP versions before 0.05 for Perl accept another account's recovery code at the…nvd · 2026-08-25
unknownUSN-8675-1: Perl vulnerabilitiesubuntu · 2026-08-25
medium[UPDATE] [medium] Red Hat Enterprise Linux (nodejs, perl): Multiple vulnerabilitiescert-bund · 2026-08-24
medium[UPDATE] [medium] Perl: Vulnerability allows code execution and information disclosurecert-bund · 2026-08-24
medium[NEW] [medium] Perl: Vulnerability enables denial of servicecert-bund · 2026-08-24