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perl-5.44.0
⭐ Starred 2013 / vars
Security Advisories (1)
CVE-2026-15534 (2026-08-09)

Perl versions through 5.45.1 have out-of-bounds heap reads and writes during regular expression matching via an undersized superlinear cache in S_regmatch. The regex engine's superlinear cache holds one bit per subject position for each participating WHILEM node, so the bit count is the subject length plus one times the number of nodes. Nothing checks that product for positive overflow of the signed 32-bit count: a 286331153 byte subject matched against a pattern with 15 participating nodes stores the count as 14, leaving a two byte cache. The cache is then indexed from the real match position and node number, so reads go past the end of the allocation, and on failure CACHEsayNO sets a bit past it. A caller that matches an attacker controlled subject of this size against a pattern of this shape can crash the process or corrupt heap memory.

NAME

vars - Perl pragma to predeclare global variable names

SYNOPSIS

use vars qw($frob @mung %seen);

DESCRIPTION

NOTE: For use with variables in the current package for a single scope, the functionality provided by this pragma has been superseded by our declarations, available in Perl v5.6.0 or later, and use of this pragma is discouraged. See "our" in perlfunc.

This pragma will predeclare all the variables whose names are in the list, allowing you to use them under use strict, and disabling any typo warnings for them.

Unlike pragmas that affect the $^H hints variable, the use vars and use subs declarations are not lexically scoped to the block they appear in: they affect the entire package in which they appear. It is not possible to rescind these declarations with no vars or no subs.

Packages such as the AutoLoader and SelfLoader that delay loading of subroutines within packages can create problems with package lexicals defined using my(). While the vars pragma cannot duplicate the effect of package lexicals (total transparency outside of the package), it can act as an acceptable substitute by pre-declaring global symbols, ensuring their availability to the later-loaded routines.

See "Pragmatic Modules" in perlmodlib.