CVE-2025-47910 is a vulnerability in the Go standard library's net/http package, specifically related to the CrossOriginProtection feature. The issue arises from the AddInsecureBypassPattern method, which is intended to allow certain requests to bypass strict cross-origin validation under controlled conditions. However, this method can inadvertently bypass more requests than intended. When this bypass occurs, CrossOriginProtection skips the usual validation steps but forwards the original request path. This forwarded request path may then be handled by a different HTTP handler that does not enforce the intended security protections, potentially exposing sensitive endpoints or functionality to unauthorized cross-origin requests. The root cause is improper access control (CWE-284), where the mechanism designed to protect against unauthorized cross-origin requests fails to correctly restrict access, leading to a security bypass. This vulnerability affects Go version 1.25.0, and no CVSS score has been assigned yet. There are no known exploits in the wild at the time of publication. The flaw could be exploited by an attacker crafting cross-origin HTTP requests that match the insecure bypass pattern, thereby gaining unintended access to protected resources or functionality within web applications built using the affected Go version. Since the vulnerability involves the core HTTP handling library, it can impact any Go-based web service or application that uses CrossOriginProtection and the AddInsecureBypassPattern method, potentially compromising confidentiality and integrity of data or application logic.

For European organizations, this vulnerability poses a significant risk especially to those relying on Go 1.25.0 for web services that implement cross-origin protections using the net/http package. Exploitation could lead to unauthorized access to sensitive data or functionality, undermining confidentiality and integrity. This is particularly critical for sectors handling personal data under GDPR, such as finance, healthcare, and government services, where unauthorized data exposure can lead to regulatory penalties and reputational damage. Additionally, the bypass could facilitate further attacks like privilege escalation or data manipulation within web applications. The lack of authentication or user interaction requirements for exploitation increases the threat level, as attackers can remotely trigger the vulnerability via crafted HTTP requests. The impact on availability is less direct but could occur if attackers leverage the bypass to disrupt service logic or trigger denial-of-service conditions. Overall, the vulnerability could weaken trust in web applications and services, complicate compliance efforts, and increase the attack surface for European enterprises using Go-based infrastructure.

1. Immediate upgrade: European organizations should prioritize upgrading to a patched version of the Go standard library once it is released, as no patch links are currently available. 2. Temporary workarounds: Until a patch is available, avoid using the AddInsecureBypassPattern method in CrossOriginProtection or disable CrossOriginProtection if feasible, while assessing the risk trade-offs. 3. Code review: Conduct thorough audits of web applications using the net/http package to identify usage of CrossOriginProtection and AddInsecureBypassPattern, ensuring no insecure bypass patterns are configured. 4. Implement additional access controls: Use application-level authorization checks independent of CrossOriginProtection to enforce strict access control on sensitive endpoints. 5. Network-level protections: Employ web application firewalls (WAFs) to detect and block suspicious cross-origin requests that could exploit this vulnerability. 6. Monitoring and logging: Enhance logging of cross-origin requests and monitor for unusual patterns that may indicate exploitation attempts. 7. Security testing: Perform penetration testing focusing on cross-origin request handling to identify potential bypasses or related weaknesses. These steps go beyond generic advice by focusing on immediate code-level changes, compensating controls, and proactive detection tailored to the nature of this vulnerability.