MIT Kerberos 5 up to 1.22.3 ldap_principal2.c berval2tl_data integer underflow

Summaryinfo

A vulnerability was found in MIT Kerberos 5 and classified as problematic. Affected by this issue is the function berval2tl_data in the library plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c. Executing a manipulation can lead to integer underflow. This vulnerability is registered as CVE-2026-11850. It is possible to launch the attack remotely. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in MIT Kerberos 5. This vulnerability affects the function berval2tl_data in the library plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c. The manipulation with an unknown input leads to a integer underflow vulnerability. The CWE definition for the vulnerability is CWE-191. The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at access.redhat.com. This vulnerability was named CVE-2026-11850 since 06/10/2026. The exploitation appears to be difficult. The attack can be initiated remotely. The exploitation requires an enhanced level of successful authentication. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/11/2026).

Upgrading to version 2.c eliminates this vulnerability.

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Productinfo

Type

• Network Authentication Software

Vendor

• MIT

Name

• Kerberos 5

Version

• 1.6
• 1.6.3 Kdc
• 1.7
• 1.14.3
• 1.17.2
• 1.18.2
• 1.18.3
• 1.18.4
• 1.18.5
• 1.19.1
• 1.19.2
• 1.19.3
• 1.20.0
• 1.20.2
• 1.21.0
• 1.21.1
• 1.21.2
• 1.21.3
• 1.22.3

License

• open-source

Website

• Vendor: http://www.mit.edu/

CPE 2.3info

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CPE 2.2info

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