CVE-2025-58189 is a security vulnerability identified in the Go programming language's standard library, specifically within the crypto/tls package responsible for handling TLS connections. The flaw arises during the TLS handshake process when ALPN negotiation fails. ALPN is used to negotiate the application protocol (e.g., HTTP/2) during the TLS handshake. If the handshake fails at this stage, the error message generated includes the ALPN protocols sent by the client. These protocols are attacker-controlled input. The vulnerability is due to improper output neutralization for logs (CWE-117), meaning the error message is logged without escaping or sanitizing this input. As a result, an attacker can craft malicious ALPN protocol strings that, when logged, could inject misleading or malicious content into log files. This log injection can corrupt log integrity, confuse monitoring tools, or hide malicious activity by forging log entries. The vulnerability affects all Go versions up to 1.25.0, with no patch currently linked. No known exploits have been reported in the wild, but the risk lies in the potential for attackers to manipulate logs, which are critical for security monitoring and forensic analysis. The absence of a CVSS score requires an assessment based on impact and exploitability factors. Since the vulnerability affects confidentiality minimally but can impact integrity and availability of logs, and exploitation requires only sending crafted ALPN protocols during handshake attempts (no authentication needed), it is a significant concern for environments relying on Go's TLS implementation for secure communications and logging.

For European organizations, the primary impact of CVE-2025-58189 is on the integrity and reliability of security logs generated by applications using the Go crypto/tls package. Log injection can mislead security analysts, obscure attack traces, and potentially allow attackers to cover their tracks or trigger false alarms. This undermines incident detection and response capabilities, increasing the risk of prolonged undetected breaches. Organizations running web servers, APIs, or microservices written in Go that utilize TLS with ALPN negotiation are particularly at risk. This includes financial institutions, government agencies, and critical infrastructure operators in Europe that rely on Go for secure communications. Although the vulnerability does not directly compromise confidentiality or availability of data, the indirect impact on security monitoring can have serious consequences. Additionally, regulatory compliance frameworks in Europe, such as GDPR and NIS Directive, emphasize the importance of accurate logging and incident response, so exploitation could lead to compliance issues and reputational damage.

1. Monitor for official patches or updates from the Go project addressing CVE-2025-58189 and apply them promptly once available. 2. Until a patch is released, implement additional log sanitization or filtering mechanisms to escape or remove suspicious characters from ALPN protocol strings before logging. 3. Review and harden logging infrastructure to detect anomalies or suspicious log entries that may indicate log injection attempts. 4. Employ defense-in-depth by using external monitoring and alerting systems that correlate multiple data sources beyond logs to detect suspicious TLS handshake failures. 5. Educate development and operations teams about this vulnerability to increase awareness and encourage cautious handling of logs involving TLS handshake errors. 6. Consider disabling ALPN negotiation if not required by the application, reducing the attack surface. 7. Conduct regular security audits and penetration testing focusing on log integrity and injection vulnerabilities in TLS implementations.