CVE-2026-85644

Summary

XS::Parse::Infix versions from 0.40 through 0.49 for Perl treat a number as an array reference.

The wrapper function XS::Parse::Infix generates for a list-associative infix operator checks whether arguments are array references, but it tests using SvRV() rather than SvROK(). SvRV() reads a union slot that only holds a referent once SvROK(sv) is true, so the guard never validates that it is a reference. For an IV or NV that slot holds the number itself, SvRV() returns the caller's value and SvTYPE() dereferences it at offset 12. This will generally result in a segmentation fault.

An application that hands the wrapper a list built from decoded input (for example, from JSON) lets whoever supplies a number in that list choose the address that the interpreter dereferences.

An ordinary string's byte 12 is rarely SVt_PVAV so the guard croaks by luck, but an attacker-crafted string carrying 0x0b there passes, and the buffer is then used as an AV head, with AvARRAY taken from bytes 16-23 and its entries pushed onto the Perl stack as live SVs.

A simple proof-of-concept uses the zip operator:

use Syntax::Operator::Zip 'zip';

my @args = ([1], 2);
zip(@args);

Affected Software

Weaknesses

• CWE-843: CWE-843 Access of Resource Using Incompatible Type ('Type Confusion')
• CWE-125: CWE-125 Out-of-bounds Read

Workarounds

For deployments that cannot upgrade, ensure that correct arguments (only array references where they are expected) are passed to list-associative operators that are defined with XS::Parse::Infix, such as those in Syntax::Operator::Zip.

ADP Enrichment

CVE Program Container

Additional References

• http://www.openwall.com/lists/oss-security/2026/09/28/14

References

• https://metacpan.org/release/PEVANS/XS-Parse-Keyword-0.50/changes
• https://metacpan.org/release/PEVANS/XS-Parse-Keyword-0.50/diff/PEVANS/XS-Parse-Keyword-0.49#src/infix.c

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