AI analysis
XS::Parse::Infix 0.40 through 0.49 builds Perl wrappers for list-associative infix operators that are supposed to accept array references, but the guard uses SvRV() without first checking that the value is a reference. A number or other non-reference can therefore be treated as an array, and the interpreter dereferences memory that was never a valid referent, which typically crashes the process with a segmentation fault. If an application feeds the wrapper a list built from decoded external input, such as JSON, the supplier of that input can influence what address is dereferenced; a crafted string can be accepted as an array and its contents pushed onto the Perl stack as live values. Perl programs that load this module and pass untrusted lists into those operators, including users of Syntax::Operator::Zip, are affected. Exploitation in the wild is not known, no separate public proof of concept is recorded, and the issue is not listed in CISA KEV.
What to do: Replace XS::Parse::Infix 0.40 through 0.49 as soon as a release outside that range is available; the advisory does not name a patched version. Until then, do not pass lists built from untrusted decoded input (such as JSON) into list-associative infix operators generated by the affected module, and review dependents such as Syntax::Operator::Zip.
Affected
| Paul Evans (CPAN) XS::Parse::Infix | 0.40 through 0.49 |
Estimated exposure
nicheNo basis for an estimate.
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
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);