CVE-2026-11850 — Krb5: krb5: integer underflow in berval2tl_data() leads to heap out-of-bounds read

Affected: Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4

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.

USN-8585-1 — krb5 vulnerabilities

Affected: Ubuntu:22.04:LTS: krb5, Ubuntu:24.04:LTS: krb5, Ubuntu:26.04:LTS: krb5

It was discovered that Kerberos had an integer underflow vulnerability in the berval2tl_data() function. An attacker could possibly use this issue to cause Kerberos to crash, resulting in a denial of service. (CVE-2026-11850)

It was discovered that Kerberos had vulnerabilities in its NegoEx mechanism parsing. A remote attacker could possibly use these issues to cause Kerberos to crash, resulting in a denial of service. (CVE-2026-40355, CVE-2026-40356)

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CVE-2026-11850 — Krb5: krb5: integer underflow in berval2tl_data() leads to heap out-of-bounds read

USN-8585-1 — krb5 vulnerabilities