CVE-2026-80490: Algorithm::AhoCorasick::XS versions through 0.04 for Perl read the haystack string length before the scalar is stringified
Algorithm::AhoCorasick::XS versions through 0.04 for Perl read the haystack string length before the scalar is stringified.
The matches, firstmatch and matchdetails methods use the TSTDSTRING typemap to translate Perl scalars (SVs) into strings via the std::string constructor, using the SvPV macro to stringify the haystack input, and the SvCUR macro to determine the length of the SV.
When the input SVs are references, integers (IVs) or floats (NVs), the SvCUR macro will return an invalid length if it is run before the input is stringified, leading to an out-of-bounds read which can abort the process.
Note that the evaluation order of arguments to std::string is unspecified. Depending on the compiler, SvCUR may be run first and lead to an abort that cannot be caught within Perl.
This can be triggered when the haystack is a numeric value, for example,
my $ac = Algorithm::AhoCorasick::XS->new( [ "11", "22" ] ); $ac->matches( 211 );
This can occur when the haystack is the result of reading data from decoded JSON or a numeric database column. It can also be triggered when using a blessed object as a haystack.
Affected Software
Event History
Frequently Asked Questions
Which inputs can trigger the out-of-bounds read?
The haystack argument can trigger the issue when it is a numeric scalar such as an integer or float, a reference, or a blessed object. Inputs produced by decoded JSON or retrieved from numeric database columns may therefore be affected.
Which methods are affected?
The affected methods are matches, first_match, and match_details when they process the haystack input.
What is the likely impact of successful triggering?
An invalid length can cause an out-of-bounds read and abort the process. Depending on compiler argument-evaluation order, the abort may not be catchable within Perl.
How can exposure be reduced if an update is not immediately available?
Ensure haystack values are explicitly converted to strings before passing them to the affected methods. In particular, normalize values originating from decoded JSON, numeric database columns, references, or objects.