CVE-2026-11850

An integer underflow vulnerability was found in MIT krb5 in the berval2tl_data() function in plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c. The function performs an unsigned subtraction (bv_len - 2) without a prior bounds check. When bv_len is 0 or 1, the subtraction wraps to a large value which is then truncated to uint16_t, yielding 0xFFFE (65534) or 0xFFFF (65535). The subsequent malloc succeeds and memcpy reads up to 65534 bytes from a 0-1 byte buffer, resulting in a heap out-of-bounds read. The attack vector involves a malicious or compromised LDAP KDB backend returning a krbExtraData attribute with bv_len < 2, triggering the underflow when the KDC or kadmind reads principal data.

• krb5 1.22.1-3 (bug https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1139821; unimportant) https://krbdev.mit.edu/rt/Ticket/Display.html?id=9206 https://github.com/krb5/krb5/commit/2a5fd83d4436583f2ddc0e193269a4d800ee45c4 No security impact, doesn't cross any security boundary, see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1139821