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perl-5.42.0
⭐ Starred 2013 / stable
Security Advisories (4)
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-2026-13221 (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-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.

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

stable - Experimental features made easy, once we know they're stable

VERSION

version 0.035

SYNOPSIS

use stable 'lexical_subs', 'bitwise';
my sub is_odd($value) { $value & 1 }

DESCRIPTION

The experimental pragma makes it easy to turn on experiments while turning off associated warnings. You should read about it, if you don't already know what it does.

Seeing use experimental in code might be scary. In fact, it probably should be! Code that uses experimental features might break in the future if the perl development team decides that the experiment needs to be altered. When experiments become stable, because the developers decide they're a success, the warnings associated with them go away. When that happens, they can generally be turned on with use feature.

This is great, if you are using a version of perl where the feature you want is already stable. If you're using an older perl, though, it might be the case that you want to use an experimental feature that still warns, even though there's no risk in using it, because subsequent versions of perl have that feature unchanged and now stable.

Here's an example: The postderef feature was added in perl 5.20.0. In perl 5.24.0, it was marked stable. Using it would no longer trigger a warning. The behavior of the feature didn't change between 5.20.0 and 5.24.0. That means that it's perfectly safe to use the feature on 5.20 or 5.22, even though there's a warning.

In that case, you could very justifiably add use experimental 'postderef' but the casual reader may still be worried at seeing that. The stable pragma exists to turn on experimental features only when it's known that their behavior in the running perl is their stable behavior.

If you try to use an experimental feature that isn't stable or available on the running version of perl, an exception will be thrown. You should also take care that you've required the version of stable that you need!

If it's not immediately obvious why, here's a bit of explanation:

  • stable comes with perl, starting with perl v5.38.

  • Imagine that v5.38 adds a feature called "florps". It will stop being experimental in v5.42.

  • The version of stable that comes with perl v5.38 can't know that the florps experiment will succeed, so you can't use stable 'florps' on the version of stable ships with v5.38, because it can't see the future!

  • You'll need to write use stable 1.234 'florps' to say that you need version 1.234 of stable, which is when florps became known to stable.

Sure, it's a little weird, but it's worth it! The documentation of this pragma will tell you what version of stable you need to require in order to use various features. See below.

At present there are only a few "stable" features:

  • bitwise - stable as of perl 5.22, available via stable 0.031

  • isa - stable as of perl 5.32, available via stable 0.031

  • lexical_subs - stable as of perl 5.22, available via stable 0.031

    Lexical subroutines were actually added in 5.18, and their design did not change, but significant bugs makes them unsafe to use before 5.22.

  • postderef - stable as of perl 5.20, available via stable 0.031

  • const_attr - stable as of perl 5.22, available via stable 0.032

  • for_list - stable as of perl 5.36, available via stable 0.032

SEE ALSO

perlexperiment contains more information about experimental features.

AUTHOR

Leon Timmermans <fawaka@gmail.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2013 by Leon Timmermans.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.