How severe is CVE-2023-41338?

CVE-2023-41338 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-41338?

CVE-2023-41338 affects the following packages: github.com/gofiber/fiber (Go), github.com/gofiber/fiber/v2 (Go). Ecosystems affected: Go.

How do I fix CVE-2023-41338?

A fix is available for CVE-2023-41338; check the affected-versions list above or the advisory for the patched release of github.com/gofiber/fiber, then make sure no transitive dependency still pins the vulnerable range.

How do I detect CVE-2023-41338 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gofiber/fiber, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2023-41338 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2023-41338 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-41338 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-41338?

CVE-2023-41338 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 52th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-41338?

CVE-2023-41338 is classified as CWE-670 (CWE-670). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2023-41338 published, and has it been updated?

CVE-2023-41338 was published on September 8, 2023 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

MEDIUM severity

CVE-2023-41338 — fiber

MEDIUMFix: gofiber/fiber@b8c9ede

CVE-2023-41338 is a medium-severity (CVSS 5.3) CWE-670 vulnerability in github.com/gofiber/fiber. A fix is available for github.com/gofiber/fiber — see the affected versions and patch details below.

Vulnerability in Ctx.IsFromLocal() in gofiber

Also known asGHSA-3q5p-3558-364fGO-2023-2052

Published

Sep 8, 2023

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

1 / 2

Exploits

None indexed

Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-41338.

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs52th percentile — riskier than 52% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

🐹github.com/gofiber/fiber🐹github.com/gofiber/fiber/v2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Impact

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()

Patches

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

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

Affected Packages

2 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/gofiber/fiber`	all versions	No fix
🐹Go	`github.com/gofiber/fiber/v2`	all versions	2.49.2`go get github.com/gofiber/fiber/v2@v2.49.2`

Affected Products

1 product · 1 configurations

Application

fibergofiber

< 2.49.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gofiber/fiber, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
A fix is available for CVE-2023-41338; check the affected-versions list above or the advisory for the patched release of github.com/gofiber/fiber, then make sure no transitive dependency still pins the vulnerable range.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact This vulnerability can be categorized as a security misconfiguration. It impacts users of our project who rely on the [ctx.IsFromLocal()](https://docs.gofiber.io/api/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(): ```go // 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.extractIPsFromHe