Fiber unauthorized access vulnerability in `ctx.IsFromLocal()`

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:

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2023-09-08 13:27:21 UTC
Updated
2023-11-05 05:01:23 UTC
GitHub reviewed
2023-09-08 13:27:21 UTC
NVD published
2023-09-08

EPSS Score

Score Percentile
0.26% 48.69%

CVSS Scores

Base score Version Severity Vector
5.3 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

CWEs

CWE id Name
CWE-670 Always-Incorrect Control Flow Implementation

Credits

  • schicho (reporter)
  • gaby (analyst)
  • efectn (analyst)
  • jozsefsallai (coordinator)
  • ReneWerner87 (analyst)

Affected packages (2)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
go github.com/gofiber/fiber <= 1.14.6
go github.com/gofiber/fiber/v2 < 2.49.2 2.49.2

References

cvelogic Threat Intelligence