Crypto Foundation Cracked: One-Byte Overflow in GNU libtasn1 (CVE-2025-13151)

A stack-based buffer overflow (CVE-2025-13151, CVSS 7.5) was disclosed in GNU libtasn1’s asn1_expand_octet_string due to unsafe string concatenation (strcpy/strcat) that can overflow a stack buffer by one byte; while this can cause memory corruption during certificate parsing or signature verification, exploitation requires malformed ASN.1 input and may be mitigated by modern protections such as stack canaries and _FORTIFY_SOURCE; a patch has been proposed and developers are urged to apply bounded string operations.