Krb5: krb5: integer underflow in berval2tl_data() leads to heap out-of-bounds read

Overview

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.

Affected

• krb5-main (all versions)
• krb5 (all versions)
• krb5 (all versions)
• krb5 (all versions)
• krb5 (all versions)
• krb5 (all versions)
• openshift/ose-rhel-coreos-8 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Workarounds

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.