Perl versions through 5.43.10 have a heap buffer overflow when compiling regular expressions with a repeated fixed string on 32-bit builds.

Perl_study_chunk in regcomp_study.c checked the size of the joined substring buffer in characters rather than bytes. For a quantified fixed substring with a large minimum count, the byte length mincount * l could overflow SSize_t, producing an undersized SvGROW allocation; the subsequent copy writes past the end of the buffer.

A caller that compiles an attacker-controlled regular expression on a 32-bit perl build triggers a heap buffer overflow at compile time.

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-8376
• https://github.com/Perl/perl5/commit/5e7f119eb2bb1181be908701f22bf7068e722f1c.patch
• http://www.openwall.com/lists/oss-security/2026/05/26/1