CVE-2026-19487: Perl versions from 5.9.4 before 5.41.9 produce incorrect regular expression match results when a stale failure flag ends the Aho-Corasick prescan early in S_find_byclass
Last updated 16 September 2026
Other sources
Perl versions from 5.9.4 before 5.41.9 produce incorrect regular expression match results when a stale failure flag ends the Aho-Corasick prescan early in Sfindbyclass
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 5.38.2-516 - Upgrade
Upgrade
debian/perlto a version that resolves this vulnerability.Fixed in 5.42.3-1 - Upgrade
Upgrade
Perlto a version that resolves this vulnerability.Fixed in 5.42.0 - Compensating control
If you cannot upgrade immediately, apply the upstream patch for CVE-2026-19487 to prevent incorrect Aho-Corasick prescan behavior in S_find_byclass (Perl 5.9.4 to before 5.41.9).
Event History
Frequently Asked Questions
What is the severity of CVE-2026-19487?
The severity of CVE-2026-19487 is rated as 37.
How do I fix CVE-2026-19487?
To fix CVE-2026-19487, update your Perl version to 5.41.9 or later.
What versions of Perl are affected by CVE-2026-19487?
CVE-2026-19487 affects Perl versions from 5.9.4 up to, but not including, 5.41.9.
What type of vulnerability is CVE-2026-19487?
CVE-2026-19487 is a software vulnerability related to incorrect regular expression match results in specific versions of Perl.
When was CVE-2026-19487 published?
CVE-2026-19487 was published on August 13, 2026.