BREW-PO4A-CVE-2026-85644 (CVE-2026-85644)
Vulnerability from osv_homebrew – Published: 2026-10-03 10:12 – Updated: 2026-10-03 10:12 – Source websiteXS::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": [
{
"ecosystem_specific": {
"fix": null,
"range_state": "affected",
"resource": "XS::Parse::Keyword::Builder",
"resource_purl": "pkg:cpan/PEVANS/XS-Parse-Keyword@0.49"
},
"package": {
"ecosystem": "Homebrew",
"name": "po4a",
"purl": "pkg:brew/po4a"
},
"ranges": [
{
"events": [
{
"introduced": "0.72"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"database_specific": {
"confidence": "medium",
"source": "matched",
"strategy": "cpansa",
"upstream_evidence": [
{
"ecosystem": "CPAN",
"key": "pkg:cpan/PEVANS/XS-Parse-Keyword@0.49",
"name": "XS-Parse-Keyword",
"resource": "XS::Parse::Keyword::Builder",
"strategy": "cpansa",
"subject_version": "0.49"
}
]
},
"details": "XS::Parse::Infix versions from 0.40 through 0.49 for Perl treat a number as an array reference.\n\nThe 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\u0027s value and SvTYPE() dereferences it at offset 12. This will generally result in a segmentation fault.\n\nAn 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.\n\nAn ordinary string\u0027s 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.\n\nA simple proof-of-concept uses the zip operator:\n\n use Syntax::Operator::Zip \u0027zip\u0027;\n\n my @args = ([1], 2);\n zip(@args);",
"id": "BREW-po4a-CVE-2026-85644",
"modified": "2026-10-03T10:12:45Z",
"published": "2026-10-03T10:12:45Z",
"references": [
{
"type": "WEB",
"url": "https://metacpan.org/release/PEVANS/XS-Parse-Keyword-0.50/changes"
},
{
"type": "WEB",
"url": "https://metacpan.org/release/PEVANS/XS-Parse-Keyword-0.50/diff/PEVANS/XS-Parse-Keyword-0.49#src/infix.c"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2026/09/28/14"
}
],
"schema_version": "1.7.3",
"summary": "XS::Parse::Infix versions from 0.40 through 0.49 for Perl treat a number as an array reference.",
"upstream": [
"CVE-2026-85644"
]
}
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