CVE-2023-41338: 
vulnerability analysis and mitigation

Fiber, an Express-inspired web framework built in Go, was found to contain a security misconfiguration vulnerability (CVE-2023-41338) in versions prior to 2.49.2. The vulnerability affects the ctx.IsFromLocal() method which is used to restrict access to localhost requests. The issue was discovered and disclosed on September 8, 2023, impacting all versions of gofiber before 2.49.2 (GitHub Advisory).

The vulnerability exists in the implementation of the IsFromLocal() method which relies on the IPs() function to check if a request originated from localhost. The IPs() function extracts IP addresses from the X-Forwarded-For header without proper validation. As a result, an attacker could set X-Forwarded-For: 127.0.0.1 in a request from a foreign host to bypass localhost restrictions. The vulnerability has been assigned a CVSS v3.1 base score of 5.3 MEDIUM (NVD).

If exploited, this vulnerability could allow unauthorized access to resources that were intended to be accessible only from localhost. The scope of impact is limited to applications that rely on the ctx.IsFromLocal() method for access control decisions (GitHub Advisory).

The vulnerability has been patched in version 2.49.2 with commit b8c9ede6. Users are strongly advised to upgrade to this version or later as there are no known workarounds to remediate this vulnerability without upgrading (GitHub Advisory).