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perl-5.45.1
⭐ Starred 2013 / Tie::Memoize
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

Tie::Memoize - add data to hash when needed

SYNOPSIS

require Tie::Memoize;
tie %hash, 'Tie::Memoize',
    \&fetch,			# The rest is optional
    $DATA, \&exists,
    {%ini_value}, {%ini_existence};

DESCRIPTION

This package allows a tied hash to autoload its values on the first access, and to use the cached value on the following accesses.

Only read-accesses (via fetching the value or exists) result in calls to the functions; the modify-accesses are performed as on a normal hash.

The required arguments during tie are the hash, the package, and the reference to the FETCHing function. The optional arguments are an arbitrary scalar $data, the reference to the EXISTS function, and initial values of the hash and of the existence cache.

Both the FETCHing function and the EXISTS functions have the same signature: the arguments are $key, $data; $data is the same value as given as argument during tie()ing. Both functions should return an empty list if the value does not exist. If EXISTS function is different from the FETCHing function, it should return a TRUE value on success. The FETCHing function should return the intended value if the key is valid.

Inheriting from Tie::Memoize

The structure of the tied() data is an array reference with elements

0:  cache of known values
1:  cache of known existence of keys
2:  FETCH  function
3:  EXISTS function
4:  $data

The rest is for internal usage of this package. In particular, if TIEHASH is overwritten, it should call SUPER::TIEHASH.

EXAMPLE

sub slurp {
  my ($key, $dir) = shift;
  open my $h, '<', "$dir/$key" or return;
  local $/; <$h>			# slurp it all
}
sub exists { my ($key, $dir) = shift; return -f "$dir/$key" }

tie %hash, 'Tie::Memoize', \&slurp, $directory, \&exists,
    { fake_file1 => $content1, fake_file2 => $content2 },
    { pretend_does_not_exists => 0, known_to_exist => 1 };

This example treats the slightly modified contents of $directory as a hash. The modifications are that the keys fake_file1 and fake_file2 fetch values $content1 and $content2, and pretend_does_not_exists will never be accessed. Additionally, the existence of known_to_exist is never checked (so if it does not exists when its content is needed, the user of %hash may be confused).

BUGS

FIRSTKEY and NEXTKEY methods go through the keys which were already read, not all the possible keys of the hash.

AUTHOR

Ilya Zakharevich mailto:perl-module-hash-memoize@ilyaz.org.