CVE-2023-41338

Fiber unauthorized access vulnerability in ctx.IsFromLocal()

Workarounds

Currently, there are no known workarounds to remediate this vulnerability without upgrading to the patched version. We strongly advise users to apply the patch as soon as it is released.

References

For further information and context regarding this security issue, please refer to the following resources:

• Mozilla Developer Network - X-Forwarded-For

This vulnerability can be categorized as a security misconfiguration. It impacts users of our project who rely on the ctx.IsFromLocal() method to restrict access to localhost requests. If exploited, it could allow unauthorized access to resources intended only for localhost.

In it's implementation it uses c.IPs():

// IPs returns a string slice of IP addresses specified in the X-Forwarded-For request header.
// When IP validation is enabled, only valid IPs are returned.
func (c *Ctx) IPs() []string {
    return c.extractIPsFromHeader(HeaderXForwardedFor)
}

Thereby, setting X-Forwarded-For: 127.0.0.1 in a request from a foreign host, will result in true for ctx.IsFromLocal()

CVE-2023-41338 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.49.2); upgrading removes the vulnerable code path.

Kodem intelligence

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This issue has been patched in v2.49.2 with commit b8c9ede6efa231116c4bd8bb9d5e03eac1cb76dc

1. What is CVE-2023-41338? CVE-2023-41338 is a medium-severity security vulnerability in github.com/gofiber/fiber (go), affecting versions <= 1.14.6. It is fixed in 2.49.2.
2. How severe is CVE-2023-41338? CVE-2023-41338 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2023-41338?
   • github.com/gofiber/fiber (go) (versions <= 1.14.6)
   • github.com/gofiber/fiber/v2 (go) (versions < 2.49.2)
4. Is there a fix for CVE-2023-41338? Yes. CVE-2023-41338 is fixed in 2.49.2. Upgrade to this version or later.
5. Is CVE-2023-41338 exploitable, and should I be worried? Whether CVE-2023-41338 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-41338 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-41338? Upgrade github.com/gofiber/fiber/v2 to 2.49.2 or later.

Other vulnerabilities in github.com/gofiber/fiber