CVE-2024-9355 is a medium-severity vulnerability identified in the Golang FIPS OpenSSL implementation. The flaw arises from the use of an uninitialized variable related to buffer length handling in FIPS mode. Specifically, a malicious actor can cause the system to return an uninitialized buffer length variable alongside a zeroed buffer. This can lead to several security issues: first, it may allow an attacker to induce false positive matches when comparing HMAC sums, by substituting a zeroed buffer in place of a legitimate pre-computed sum. This undermines the integrity verification process, potentially allowing unauthorized data to be accepted as valid. Second, the vulnerability can cause a derived cryptographic key to be all zeros instead of a securely generated unpredictable value. This severely weakens cryptographic operations relying on such keys, including those in the Go TLS stack, potentially compromising confidentiality and integrity of communications. The vulnerability requires local access (AV:L) with low privileges (PR:L), no user interaction (UI:N), and has a high attack complexity (AC:H), indicating exploitation is non-trivial but possible under certain conditions. The scope is unchanged (S:U), but the impact on confidentiality and integrity is high (C:H/I:H), with a low impact on availability (A:L). No known exploits are currently reported in the wild. The vulnerability affects the cryptographic core of Golang’s FIPS OpenSSL integration, which is critical for secure communications and data protection in applications using this stack.

For European organizations, this vulnerability poses significant risks, especially those relying on Golang applications that utilize FIPS-compliant OpenSSL cryptographic modules. The potential for false positive HMAC matches can lead to acceptance of tampered or malicious data, undermining data integrity and trust in secure communications. The possibility of zeroed derived keys compromises the confidentiality of encrypted data and TLS sessions, potentially exposing sensitive information or enabling man-in-the-middle attacks. Sectors such as finance, healthcare, government, and critical infrastructure in Europe, which often require FIPS compliance for regulatory reasons, may be particularly impacted. The vulnerability could lead to breaches of GDPR requirements concerning data protection and integrity. Although exploitation requires local access and has high complexity, insider threats or attackers who gain limited access could leverage this flaw to escalate privileges or compromise secure communications. The lack of known exploits suggests limited immediate threat, but the critical nature of cryptographic failures warrants urgent attention.

European organizations should prioritize updating or patching the Golang FIPS OpenSSL components as soon as vendor patches become available. In the interim, organizations should audit their use of Golang cryptographic libraries to identify affected versions and configurations running in FIPS mode. Restrict local access to systems running vulnerable Golang applications to trusted personnel only, and enhance monitoring for anomalous behavior indicative of exploitation attempts. Implement additional cryptographic verification layers where possible, such as application-level integrity checks independent of the vulnerable HMAC comparisons. Conduct thorough code reviews and penetration testing focused on cryptographic operations within Golang applications. For critical systems, consider temporary mitigation by disabling FIPS mode if operationally feasible and secure alternative cryptographic libraries until patches are applied. Maintain strict access controls and network segmentation to limit potential attacker movement. Finally, keep abreast of vendor advisories and threat intelligence updates regarding this vulnerability.