/ 
perl-5.40.5-RC1
⭐ Starred 2013 / perldelta
Security Advisories (4)
CVE-2026-13221 (2026-07-13)

Perl versions through 5.43.9 produce silently incorrect regular expression matches when an alternation of more than 65535 fixed string branches is compiled into a trie in Perl_study_chunk. When such branches are combined into a trie, the delta between the first branch and the shared tail is stored in a 16-bit field. A branch count above 65535 overflows the field, and the trie's match decision table is truncated with no warning or error. A pattern of this shape produces false positive matches (matching strings it should not) and false negative matches (failing to match strings it should). When such a pattern gates an access or filtering decision, the result is wrong.

CVE-2025-40909 (2025-05-30)

Perl threads have a working directory race condition where file operations may target unintended paths. If a directory handle is open at thread creation, the process-wide current working directory is temporarily changed in order to clone that handle for the new thread, which is visible from any third (or more) thread already running. This may lead to unintended operations such as loading code or accessing files from unexpected locations, which a local attacker may be able to exploit. The bug was introduced in commit 11a11ecf4bea72b17d250cfb43c897be1341861e and released in Perl version 5.13.6

CVE-2026-57432 (2026-07-13)

Perl versions through 5.43.10 have an integer overflow in S_measure_struct leading to an out-of-bounds heap read in pack and unpack. S_measure_struct adds each item's size times its repeat count to a running total with no overflow check, so a large repeat count in a pack or unpack template wraps the signed SSize_t total negative. The @, X, and x position codes then guard their moves with a signed length comparison that passes when the length is negative, advancing the buffer pointer out of bounds. A template derived from untrusted input can read heap memory past the buffer and return it to the caller.

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.

NAME

perldelta - what is new for perl v5.40.5

DESCRIPTION

This document describes differences between the 5.40.4 release and the 5.40.5 release.

If you are upgrading from an earlier release such as 5.40.3, first read perl5404delta, which describes differences between 5.40.3 and 5.40.4.

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 5.40.4. 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 3.02_001 to 3.12.

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

  • Compress::Raw::Bzip2 has been upgraded from version 2.212 to 2.218.

  • HTTP::Tiny has been upgraded from version 0.088 to 0.096.

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

  • IO::Compress has been upgraded from version 2.212 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_40 to 5.20260802_40.

  • Socket has been upgraded from version 2.038 to 2.041.

    This fixes CVE-2026-12087.

  • Storable has been upgraded from version 3.32 to 3.32_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 5.40.5 represents approximately 4 months of development since Perl 5.40.4 and contains approximately 4,100 lines of changes across 130 files from 15 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 2,000 lines of changes to 64 .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 5.40.5:

Aristotle Pagaltzis, Chris 'BinGOs' Williams, David Mitchell, 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.