PERL5423DELTA(1)

NAME
perldelta - what is new for perl v5.42.3

DESCRIPTION
This document describes differences between the 5.42.2 release and the 5.42.3 release.

If you are upgrading from an earlier release such as 5.42.1, first read perl5422delta, which describes differences between 5.42.1 and 5.42.2.

Security

  CVE-2026-8376 - Buffer overflow in Perl_study_chunk
Perl_study_chunk in regcomp_study.c checked the size of the joined substring buffer in characters rather than bytes. On 32-bit builds, this can lead to an integer overflow of the size of the buffer leading to out-of-bounds writes.

  CVE-2026-57432 - Buffer overflow in S_measure_struct
If you call "pack" or "unpack" to operate on a structure whose computed size is too large to fit in memory, an integer overflow could happen that would result in a buffer overflow. This usually happens as a result of embedding a large number as the repeat count for an item.

  CVE-2026-13221 - Regex trie 16-bit field overflow
The trie optimization in the regex engine could overflow in an alternation with more than ~65k branches. This could cause both false positives and false negatives on such regular expressions.

Incompatible Changes
There are no changes intentionally incompatible with 5.42.2. If any exist, they are bugs, and we request that you submit a report. See "Reporting Bugs" below.

Modules and Pragmata

  Updated Modules and Pragmata

•   Archive::Tar has been upgraded from version 3.04 to 3.12.

    This fixes CVE-2026-9538, CVE-2026-42496, and CVE-2026-42497.

•   Compress::Raw::Bzip2 has been upgraded from version 2.213 to 2.218.

•   HTTP::Tiny has been upgraded from version 0.090 to 0.096.

    This fixes CVE-2026-7010 and CVE-2026-7017.

•   IO::Compress has been upgraded from version 2.213 to 2.223.

    This fixes CVE-2025-15649, CVE-2026-48961, CVE-2026-48962, and CVE-2026-48959.

•   Module::CoreList has been upgraded from version 5.20260329_42 to 5.20260802_42.

•   Socket has been upgraded from version 2.038 to 2.041.

    This fixes CVE-2026-12087.

•   Storable has been upgraded from version 3.37 to 3.37_01.

    This fixes CVE-2026-57433.

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>.

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

•   Pack template structure size is too large

    (F) You called "pack" or "unpack" to operate on a structure, whose computed size is too large to fit in memory. This usually happens as a result of embedding a large number as the repeat count for an item.

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

Acknowledgements
Perl 5.42.3 represents approximately 4 months of development since Perl 5.42.2 and contains approximately 4,000 lines of changes across 120 files from 14 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 1,700 lines of changes to 59 .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 5.42.3:

Aristotle Pagaltzis, Chris 'BinGOs' Williams, E. Choroba, Eric Herman, Karen Etheridge, Karl Williamson, Leon Timmermans, Paul Evans, Paul Marquess, Philippe Bruhat (BooK), Richard Leach, Steve Hay, 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.