CVE-2024-9355 is a vulnerability discovered in the Golang FIPS OpenSSL integration, specifically related to the use of an uninitialized variable that affects cryptographic operations in FIPS mode. The flaw causes an uninitialized buffer length variable to be returned with a zeroed buffer, which can lead to incorrect cryptographic behavior. One key impact is the possibility of a false positive match when comparing a trusted computed HMAC sum against an untrusted input sum if the attacker can supply a zeroed buffer instead of a legitimate pre-computed sum. This undermines the integrity verification process, potentially allowing attackers to bypass HMAC validation. Furthermore, the vulnerability can cause derived cryptographic keys to be all zeros rather than unpredictable values, severely weakening cryptographic protections. Since the Go TLS stack relies on these cryptographic primitives, this vulnerability may cascade into TLS communications, risking confidentiality and integrity of data in transit. The CVSS 3.1 score is 6.5 (medium severity), reflecting the requirement for local access (AV:L), high attack complexity (AC:H), and low privileges (PR:L), but no user interaction (UI:N). No patches or exploits are currently publicly available, but the flaw is recognized and published by Red Hat and CISA. The vulnerability highlights the critical importance of proper initialization in cryptographic code, especially in FIPS-validated modules where strict compliance and security guarantees are expected.

The vulnerability can significantly impact organizations relying on Golang applications that use the FIPS OpenSSL module for cryptographic operations. The potential for false positive HMAC matches can allow attackers to bypass integrity checks, leading to unauthorized data acceptance or tampering going undetected. The possibility of derived keys being all zeros compromises cryptographic strength, potentially allowing attackers to decrypt or forge TLS communications. This undermines confidentiality and integrity of sensitive data transmitted over networks. Although exploitation requires local access with low privileges and high attack complexity, environments with multi-tenant or shared access systems could be at risk. The flaw could affect internal services, APIs, or microservices using Go with FIPS mode enabled, especially in regulated industries requiring FIPS compliance such as government, finance, and healthcare. The absence of known exploits reduces immediate risk, but the vulnerability should be addressed promptly to prevent future exploitation and maintain trust in cryptographic assurances.

Organizations should monitor for official patches or updates from Golang and OpenSSL maintainers and apply them promptly once available. In the interim, review and audit all cryptographic operations using Golang FIPS OpenSSL to detect anomalous HMAC validation results or suspicious zeroed keys. Consider disabling FIPS mode temporarily if feasible and if it does not violate compliance requirements, to mitigate risk until patched. Implement additional integrity checks or layered cryptographic verification where possible to detect false positives. Restrict local access to systems running vulnerable Golang FIPS OpenSSL versions to trusted administrators only, minimizing the attack surface. Conduct thorough testing of TLS communications and key derivation processes to identify any irregularities. Maintain up-to-date inventory of Golang applications using FIPS OpenSSL to prioritize remediation. Educate developers and security teams about the risks of uninitialized variables in cryptographic code to prevent similar issues in the future.