CVE-2024-9355 is a medium-severity vulnerability identified in the Golang FIPS OpenSSL implementation. The flaw arises from the use of an uninitialized buffer length variable in FIPS mode, which can lead to the return of a zeroed buffer length instead of a properly initialized value. This vulnerability can be exploited by a malicious actor to cause incorrect cryptographic operations, including forcing a false positive match between non-equal hashes during HMAC sum comparisons. Specifically, an attacker who can supply a zeroed buffer in place of a pre-computed HMAC sum may trick the system into accepting invalid authentication codes. Additionally, the vulnerability can cause a derived cryptographic key to be all zeros rather than a securely generated unpredictable value. Such weaknesses undermine the integrity and confidentiality guarantees provided by cryptographic functions and may have cascading effects on the Go TLS stack, potentially compromising secure communications. The vulnerability requires local access (AV:L) with high attack complexity (AC:H) and low privileges (PR:L), but no user interaction (UI:N). The scope is unchanged (S:U), and the impact on confidentiality and integrity is high, with a low impact on availability. No known exploits are currently reported in the wild, and no specific affected versions or patches have been detailed yet.

For European organizations, this vulnerability poses a significant risk to the security of applications and services relying on Golang's FIPS OpenSSL cryptographic libraries, especially those implementing TLS for secure communications. The potential for false positive HMAC matches and zeroed derived keys can lead to unauthorized access, data tampering, or interception of sensitive information. Critical sectors such as finance, healthcare, government, and telecommunications that depend on strong cryptographic assurances could face data breaches or regulatory non-compliance if exploited. The flaw could also undermine trust in digital signatures and authentication mechanisms, impacting secure transactions and communications. Given the medium CVSS score and the requirement for local access, the threat is more relevant in environments where attackers can gain some level of system access, such as multi-tenant cloud services or compromised internal networks. The cascading impact on the Go TLS stack could affect a broad range of Go-based applications widely used in Europe, increasing the potential attack surface.

European organizations should proactively audit their use of Golang FIPS OpenSSL libraries and monitor for updates or patches addressing CVE-2024-9355. Until patches are available, organizations should restrict local access to systems running vulnerable versions, enforce strict privilege separation, and implement robust monitoring for anomalous cryptographic operations or authentication failures. Code reviews and testing should focus on cryptographic key derivation and HMAC verification routines to detect unexpected zeroed buffers or mismatches. Where feasible, consider temporarily disabling FIPS mode or using alternative cryptographic libraries with verified security until a fix is applied. Additionally, organizations should enhance network segmentation and endpoint security controls to limit the ability of attackers to gain local access. Incident response plans should be updated to include detection and remediation steps for cryptographic anomalies related to this vulnerability.