CVE-2024-9355 is a vulnerability identified in the Golang implementation of FIPS-compliant OpenSSL cryptographic libraries. The root cause is the use of an uninitialized variable that leads to a zeroed buffer length being returned when operating in FIPS mode. This can cause multiple cryptographic failures: first, it may allow an attacker to cause a false positive match between a trusted computed HMAC sum and an untrusted input sum by substituting a zeroed buffer in place of a legitimate pre-computed sum. This undermines the integrity verification process critical to secure communications. Second, the flaw can cause derived cryptographic keys to be all zeros rather than unpredictable values, severely weakening cryptographic strength and potentially allowing attackers to predict or reproduce keys. These issues have direct implications for the Go TLS stack, which relies on these cryptographic primitives for secure transport layer security. The vulnerability requires local access with low privileges and has a high attack complexity, meaning exploitation is non-trivial and likely limited to targeted scenarios. No user interaction is required, and the scope is unchanged, affecting only the local system where the vulnerable library is used. No patches or exploits are currently publicly available, but the flaw represents a significant risk to cryptographic assurances in affected environments.

For European organizations, this vulnerability poses a risk to the confidentiality and integrity of sensitive data transmitted or stored using Go applications that rely on FIPS OpenSSL cryptographic modules. The potential for false positive HMAC matches can allow attackers to bypass integrity checks, leading to unauthorized data manipulation or acceptance of malicious data. The possibility of zeroed derived keys compromises cryptographic strength, potentially exposing encrypted communications or stored secrets to compromise. This is particularly critical for sectors handling sensitive personal data under GDPR, such as finance, healthcare, and government services. The impact on TLS communications could disrupt secure channels, leading to data breaches or interception. However, the requirement for local access and high attack complexity limits widespread exploitation, making targeted attacks more likely. Organizations using Go in cloud-native applications, microservices, or internal tooling with FIPS mode enabled are at heightened risk. The absence of known exploits provides a window for mitigation but also necessitates proactive vulnerability management.

European organizations should immediately audit their use of Golang FIPS OpenSSL libraries, especially in applications handling sensitive cryptographic operations. Until patches are released, consider disabling FIPS mode if feasible and safe, or restrict access to systems running vulnerable versions to trusted administrators only. Implement strict access controls and monitoring to detect any anomalous local activity that could indicate exploitation attempts. Review and enhance cryptographic key management practices, including regenerating keys and secrets that may have been derived using the vulnerable code. Employ defense-in-depth strategies such as network segmentation and application-layer encryption to reduce reliance on the vulnerable cryptographic primitives. Stay informed on vendor advisories and apply patches promptly once available. Conduct thorough testing of TLS implementations to detect any abnormal behavior or failed integrity checks. Engage with software vendors and open-source communities to accelerate patch development and deployment. Finally, incorporate this vulnerability into incident response plans to ensure rapid containment if exploitation is detected.