Is CVE-2026-91767 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-91767?

CVE-2026-91767 has a CVSS v3 severity of MEDIUM (6.5).

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CVE-2026-91767

Description

php_openssl_matches_wildcard_name() in ext/openssl/xp_ssl.c underflows the length argument passed to memchr() when a TLS server certificate presents a wildcard name whose literal characters are together longer than the hostname being verified. A malicious server presenting such a certificate makes the PHP client read up to SIZE_MAX bytes past the end of a heap allocation. The path is reachable from any default client stream, because verify_peer_name is enabled by default.