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perl-5.43.6
⭐ Starred 2013 / perldelta
Security Advisories (2)
CVE-2026-8376 (2026-05-25)

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.

CVE-2026-4176 (2026-03-29)

Perl versions from 5.9.4 before 5.40.4-RC1, from 5.41.0 before 5.42.2-RC1, from 5.43.0 before 5.43.9 contain a vulnerable version of Compress::Raw::Zlib. Compress::Raw::Zlib is included in the Perl package as a dual-life core module, and is vulnerable to CVE-2026-3381 due to a vendored version of zlib which has several vulnerabilities, including CVE-2026-27171. The bundled Compress::Raw::Zlib was updated to version 2.221 in Perl blead commit c75ae9cc164205e1b6d6dbd57bd2c65c8593fe94.

NAME

perldelta - what is new for perl v5.43.6

DESCRIPTION

This document describes differences between the 5.43.5 release and the 5.43.6 release.

If you are upgrading from an earlier release such as 5.43.4, first read perl5435delta, which describes differences between 5.43.4 and 5.43.5.

Deprecations

  • Using goto to jump into the body of a loop or other block construct from outside is no longer permitted. [GH #23618]

Modules and Pragmata

Updated Modules and Pragmata

Documentation

Changes to Existing Documentation

We have attempted to update the documentation to reflect the changes listed in this document. If you find any we have missed, open an issue at https://github.com/Perl/perl5/issues.

Additionally, the following selected changes have been made:

perlxs

  • The reference manual for writing Perl XS code has been completely rewritten and modernized. It is about twice the size of the old file, and promotes more modern XS syntax, such as ANSI signatures.

Diagnostics

The following additions or changes have been made to diagnostic output, including warnings and fatal error messages. For the complete list of diagnostic messages, see perldiag.

New Diagnostics

New Errors

Changes to Existing Diagnostics

  • The error Unrecognised parameters for "%s" constructor: %s has been changed to Unrecognized parameters for "%s" constructor: %s.

  • The deprecation warning Attempt to call undefined %s method with arguments ("%s"%s) via package "%s" (Perhaps you forgot to load the package?) has been changed to Attempt to call undefined %s method with arguments via package "%s" (Perhaps you forgot to load the package?) and is now a fatal error.

Testing

Tests were added and changed to reflect the other additions and changes in this release.

Platform Support

Platform-Specific Notes

Windows

A compilation error in unthreaded builds using MSVC introduced in Perl 5.43.5 has been fixed. [GH #23952]

Internal Changes

  • Perl_sv_backoff, which undoes the OOK string offset mechanism now only moves the string buffer contents to the start of the buffer if `SvOK(sv)` is true. Historically, the buffer contents were always moved, but if the buffer contents are defunct and no longer required, doing that incurs an unnecessary cost proportional to the size of the shifted contents.

    (The assumption in this change is that `SvOK(sv)` is a valid indicator of whether the string buffer contents are "live" or not.)

    See [GH #23967] for an example of where such a copy was noticeable.

  • The XS parser, ExtUtils::ParseXS, has been further extensively restructured internally. Most of these changes shouldn't be visible externally, but might affect XS code which was using invalid or unsupported syntax. Several minor bug-fixes were included.

Selected Bug Fixes

  • Regexes which include both a sub-pattern (e.g. (??{...}) or (?&FOO)) and a cut (i.e. (?>...)) could sometimes cause a premature scope exit in other code during a match. For example, in something like (?{ local $x = ... }), the local might have been unwound before the pattern has finished matching. [GH #16197]

  • DB::sub is not meant to be called for sub calls from the DB package, but called to overloaded subs for overloaded values used in the DB package would result in calls in DB::sub. Fixed the check for the current package in amagic_call(). [GH #24001]

  • pregexec() handles zero-length strings again, fixing an assert failure in Package-Stash-XS (which Moose depends upon). This had been broken in Perl 5.43.4. [GH #23903]

Acknowledgements

Perl 5.43.6 represents approximately 4 weeks of development since Perl 5.43.5 and contains approximately 25,000 lines of changes across 330 files from 17 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 11,000 lines of changes to 280 .pm, .t, .c and .h files.

Perl continues to flourish into its fourth decade thanks to a vibrant community of users and developers. The following people are known to have contributed the improvements that became Perl 5.43.6:

Bartosz Jarzyna, Chad Granum, Chris 'BinGOs' Williams, Dan Book, David Mitchell, Eric Herman, James E Keenan, James Raspass, Karl Williamson, Max Maischein, Paul Evans, Philippe Bruhat (BooK), Richard Leach, Steve Hay, TAKAI Kousuke, Thibault Duponchelle, Tony Cook.

The list above is almost certainly incomplete as it is automatically generated from version control history. In particular, it does not include the names of the (very much appreciated) contributors who reported issues to the Perl bug tracker.

Many of the changes included in this version originated in the CPAN modules included in Perl's core. We're grateful to the entire CPAN community for helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see the AUTHORS file in the Perl source distribution.

Reporting Bugs

If you find what you think is a bug, you might check the perl bug database at https://github.com/Perl/perl5/issues. There may also be information at https://www.perl.org/, the Perl Home Page.

If you believe you have an unreported bug, please open an issue at https://github.com/Perl/perl5/issues. Be sure to trim your bug down to a tiny but sufficient test case.

If the bug you are reporting has security implications which make it inappropriate to send to a public issue tracker, then see "SECURITY VULNERABILITY CONTACT INFORMATION" in perlsec for details of how to report the issue.

Give Thanks

If you wish to thank the Perl 5 Porters for the work we had done in Perl 5, you can do so by running the perlthanks program:

perlthanks

This will send an email to the Perl 5 Porters list with your show of thanks.

SEE ALSO

The Changes file for an explanation of how to view exhaustive details on what changed.

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.