Package: perl
Version: 5.40.1-6
Severity: important
Tags: security upstream trixie
Control: close -1 5.42.0-1
X-Debbugs-Cc: [email protected], Debian Security Team <[email protected]>
Hi,
The following vulnerability was published for perl.
It's fixed in sid + forky with Perl 5.42, but still presumably applies
to trixie and older. So filing a bug to track the issue.
The issue is already in the security tracker [1]. Salvatore & co: could
you please add a reference to this bug.
I expect this is suitable for a trixie point release once I get that
far with my TODO list.
CVE-2026-19487 [2]
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
Description
-----------
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.
The prescan walks the subject for positions where the full pattern
could match, and the engine tries it from the leftmost one recorded. A
failing transition sets the failed flag, and a later successful
transition does not clear it, so the prescan reads the stale flag as a
failure and stops before it can record a candidate that starts earlier.
It takes a subject where one candidate is recorded and a later
character then forces a fallback through a fail link that succeeds.
Example:
"ABCDE" =~ m/ABCF|BCDE|C/; # matches C at offset 2, not BCDE
"ABCDE" =~ m/ABCF|BCDE|C(G)/; # no match, BCDE missed
An alternation like this can miss input it should match, or match it on
the wrong branch, so an access or filtering decision made from the
result can be wrong.
[1] https://security-tracker.debian.org/tracker/CVE-2026-19487
[2] https://lists.security.metacpan.org/cve-announce/msg/42658992/
--
Niko
