CVE-2022-45142: Heimdal GSSAPI/ARCFOUR Vulnerability Due to Logic Inversion in Validation of Message Integrity Codes

A new vulnerability, CVE-2022-45142, has recently been identified in the Heimdal implementation of Generic Security Services Application Program Interface (GSSAPI) mechanism, specifically affecting the ARCFour (ARC4) encryption algorithm. This post provides an in-depth analysis of the vulnerability, detailing the affected code, backported patches, and the potential exploit scenario. Additionally, links to the original references and resources for further information are provided.

Background

In a previous vulnerability, CVE-2022-3437, a fix was implemented which changed the memcmp function to be constant time, and added "!= " comparisons as a workaround for a compiler bug. However, when these patches were backported to the heimdal-7.7.1 and heimdal-7.8. branches (and possibly other branches), a logic inversion was introduced, causing the validation of message integrity codes (MICs) in the GSSAPI/arcfour implementation to be inverted.

Code Snippet

The code snippet below demonstrates the affected part of the implementation in the GSSAPI/arcofour. The incorrect logic inversion can be seen in the comparison with "!= ":

/* Previously, in CVE-2022-3437 */
if (CT_memcmp(&ctx->seq_number, &seq_number, 4) == )

/* After the backported patch in heimdal-7.7.1 and heimdal-7.8. */
if (CT_memcmp(&ctx->seq_number, &seq_number, 4) != )

Exploit Details

The vulnerability introduced by the logic inversion in the GSSAPI/arcfour implementation allows an attacker to bypass the validation of Message Integrity Codes (MICs). In turn, this could enable attackers to potentially tamper with or forge messages, leading to unauthorized access or privilege escalation attacks in affected systems.

As the vulnerability affects the ARCFour (ARC4) encryption algorithm in Heimdal's GSSAPI implementation, systems that utilize this implementation for authentication or data protection may be at risk of compromise. System administrators are strongly advised to apply the available patches and updates to mitigate this vulnerability.

Original References

1. Heimdal Security Advisory: Link to Heimdal Security advisory for CVE-2022-45142
2. CVE-2022-45142 Details: Link to the CVE details page for CVE-2022-45142
3. Heimdal Source Repository: Link to the affected Heimdal source code repository (heimdal-7.7.1 and heimdal-7.8. branches)

Conclusion

CVE-2022-45142 is a significant vulnerability in the Heimdal GSSAPI/ARCFOUR implementation, resulting from a logic inversion introduced during the backporting of patches for CVE-2022-3437. This vulnerability can potentially be exploited by attackers to bypass the validation of Message Integrity Codes (MICs) in affected systems. To mitigate the risks associated with this vulnerability, system administrators are urged to apply the appropriate patches and updates as soon as possible.

Stay informed about the latest security vulnerabilities and ensure your systems are up-to-date to minimize the risk of compromise.

Timeline

Published on: 03/06/2023 23:15:00 UTC
Last modified on: 03/13/2023 18:02:00 UTC