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perl-5.43.9
⭐ Starred 2013 / Internals
Security Advisories (3)
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-2026-8376 (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

Internals - Reserved special namespace for internals related functions

SYNOPSIS

$is_ro= Internals::SvREADONLY($x)
$refcnt= Internals::SvREFCNT($x)
hv_clear_placeholders(%hash);
if (Internals::stack_refcounted & 1) { .... }

DESCRIPTION

The Internals namespace is used by the core Perl development team to expose certain low level internals routines for testing and other purposes.

In theory these routines were not and are not intended to be used outside of the perl core, and are subject to change and removal at any time.

In practice people have come to depend on these over the years, despite being historically undocumented, so we will provide some level of forward compatibility for some time. Nevertheless you can assume that any routine documented here is experimental or deprecated and you should find alternatives to their use.

FUNCTIONS

SvREFCNT(THING [, $value])

Historically Perl has been a refcounted language. This means that each variable tracks how many things reference it, and when the variable is no longer referenced it will automatically free itself. In theory Perl code should not have to care about this, and in a future version Perl might change to some other strategy, although in practice this is unlikely.

This function allows one to violate the abstraction of variables and get or set the refcount of a variable, and in generally is really only useful in code that is testing refcount behavior.

*NOTE* You are strongly discouraged from using this function in non-test code and especially discouraged from using the set form of this function. The results of doing so may result in segmentation faults or other undefined behavior.

SvREADONLY(THING, [, $value])

Set or get whether a variable is readonly or not. Exactly what the readonly flag means depend on the type of the variable affected and the version of perl used.

You are strongly discouraged from using this function directly. It is used by various core modules, like Hash::Util, and the constant pragma to implement higher-level behavior which should be used instead.

See the core implementation for the exact meaning of the readonly flag for each internal variable type.

hv_clear_placeholders(%hash)

Clear any placeholders from a locked hash. Should not be used directly. You should use the wrapper functions provided by Hash::Util instead. As of 5.25 also available as Hash::Util::_clear_placeholders(%hash)

stack_refcounted

Returns an integer indicating whether the perl binary has been configured and built with an argument stack which reference-counts any items pushed onto it. The value should be treated as flag bits. Currently only bit 0 is used, indicating that PERL_RC_STACK was enabled during the build.

AUTHOR

Perl core development team.

SEE ALSO

perlguts Hash::Util constant universal.c