CVE-2022-45142 in Heimdal
Summary
by MITRE • 03/07/2023
The fix for CVE-2022-3437 included changing memcmp to be constant time and a workaround for a compiler bug by adding "!= 0" comparisons to the result of memcmp. When these patches were backported to the heimdal-7.7.1 and heimdal-7.8.0 branches (and possibly other branches) a logic inversion sneaked in causing the validation of message integrity codes in gssapi/arcfour to be inverted.
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Analysis
by VulDB Data Team • 03/29/2025
The vulnerability identified as CVE-2022-45142 represents a critical flaw in the Heimdal Kerberos implementation that specifically affects the Generic Security Services Application Programming Interface (GSS-API) arcfour message integrity code validation mechanism. This issue emerged from a problematic backport of security fixes intended to address CVE-2022-3437, which focused on implementing constant-time memory comparison operations to prevent timing attacks. The original fix was designed to mitigate side-channel vulnerabilities by ensuring that memory comparison operations execute in constant time regardless of input differences, thereby preventing attackers from inferring information through timing variations. However, during the backporting process to older Heimdal versions including 7.7.1 and 7.8.0, a critical logical error was introduced that fundamentally inverted the validation logic for message integrity codes.
The technical flaw manifests in how the patched memcmp function handles its return values during message integrity code validation within the gssapi/arcfour subsystem. The original implementation correctly implemented constant-time comparisons to prevent timing-based attacks, but the backported code introduced an erroneous logic inversion that caused the system to validate message integrity codes in the reverse manner. This means that when a message integrity code should be accepted, the system incorrectly rejects it, and conversely, when a message integrity code should be rejected, the system incorrectly accepts it. The vulnerability specifically impacts the arcfour encryption algorithm implementation within Heimdal's GSS-API, where the validation mechanism for ensuring message integrity has been inverted, potentially allowing attackers to bypass security checks without detection.
The operational impact of this vulnerability is severe as it undermines the fundamental security guarantees provided by message integrity protection mechanisms in Kerberos authentication systems. Systems using affected Heimdal versions with arcfour encryption are vulnerable to message integrity code manipulation attacks, where malicious actors could potentially forge or modify authenticated messages without detection. This creates a significant risk in environments where Kerberos is used for secure authentication and authorization, as the integrity of communications between clients and servers could be compromised. The vulnerability affects the core cryptographic validation processes that ensure messages have not been tampered with during transmission, potentially allowing attackers to execute unauthorized actions or access sensitive information through manipulated authentication flows.
This vulnerability aligns with CWE-298, which addresses the issue of improper validation of security-relevant information, and represents a classic case of logic inversion in security-critical code paths. The flaw demonstrates the dangers of complex backporting operations in security software, where seemingly minor changes can introduce critical logical errors that compromise fundamental security properties. From an ATT&CK perspective, this vulnerability maps to T1552.001 (Unsecured Credentials) and T1071.004 (Application Layer Protocol: DNS) as it affects the integrity of authentication mechanisms and could enable credential theft or unauthorized access through manipulated message flows. Organizations using affected Heimdal versions should immediately apply patches or updates that correct the logic inversion in the message integrity code validation, and consider implementing additional monitoring for unusual authentication patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of thorough regression testing when backporting security fixes to maintain the integrity of cryptographic implementations.