Crypt::OpenSSL::X509 CVE-2026-58102

Exploitation requires that the target Perl application parse an attacker-supplied X.509 certificate AND invoke one of the OID/long-name extension-enumeration functions on it - specifically extensions(), extensions_by_long_name(), extensions_by_oid(), or has_extension_oid() - since these drive the vulnerable hv_exts() long-OID path. The malicious certificate must contain at least one extension whose textual OID exceeds the fixed 129-byte buffer. What LIMITS exploitation: applications that never call these functions on untrusted certificates are not exposed, and those that use extensions_by_name() (static short-name path) are explicitly unaffected; the impact is bounded to disclosing adjacent heap memory or triggering a crash rather than code execution (SSVC Technical Impact: partial). No authentication is required (PR:N) because certificates are typically accepted from unauthenticated peers, but the module version must be earlier than 2.1.3.

The raw CVSS 3.1 score is 9.1 (AV:N/AC:L/PR:N/UI:N/C:H/I:N/A:H), which looks critical, but the multi-source signals temper that: CISA SSVC rates Exploitation as 'none', Automatable 'yes', and Technical Impact only 'partial' - consistent with an information-disclosure/crash bug rather than code execution. There is no KEV listing and no EPSS score supplied, and no public exploit is identified at time of analysis, so this is not evidence of active exploitation. The AV:N/PR:N/UI:N metrics are technically defensible because a certificate can arrive over the network with no authentication, but they understate a real precondition: the victim application must actually call one of the vulnerable extension-enumeration functions on the attacker-controlled certificate. The impact is also narrower than C:H suggests - the leak is bounded adjacent-heap memory surfaced as a hash key, and A:H reflects a possible crash if the over-read hits unmapped memory rather than reliable denial of service. Net: a genuine, easy-to-trigger memory-safety defect worth patching promptly wherever untrusted certificates are parsed, but 'Automatable: yes / Exploitation: none / Technical Impact: partial' argues this is a moderate real-world priority, not an emergency, absent evidence of exploitation.

An attacker crafts an X.509 certificate containing an extension whose OID renders to a textual form longer than 129 bytes and presents it to a Perl service (for example a TLS client-cert validator, S/MIME processor, or certificate-inspection tool) that enumerates extensions via extensions() or has_extension_oid(). When the module builds the extension hash, OBJ_obj2txt()'s length is used as the hash-key length, reading past the buffer and returning adjacent heap bytes as the key - which the application may log, store, or return, disclosing process memory or crashing the parser. No public exploit is identified at time of analysis, and the low attack complexity (AC:L) means only a single malicious certificate is needed.