CRLF vulnerability in Fiber

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.2 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS

• CVE-2020-15111: 0.86% estimated exploitation activity in the next 30 days; percentile 58.60 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The filename that is given in c.Attachment() is not escaped, and therefore vulnerable for a CRLF injection attack. I.e. an attacker could upload a custom filename and then give the link to the victim. With this filename, the attacker can change the name of the downloaded file, redirect to another site, change the authorization header, etc. Steps to reproduce Patches This issue has been patched in v1.12.6 with commit 579 escaping the filename by default. Workarounds You could of course serialize the input yourself before passing it to ctx.Attachment(), this is actually a good practice by default. But in case you forget, we got you covered 👍 References A CRLF injection attack is one of several types of injection attacks. It can be used to escalate to more malicious attacks such as Cross-site Scripting (XSS), page injection, web cache poisoning, cache-based defacement, and more. A CRLF injection vulnerability exists if an attacker can inject the CRLF characters into a web…

Published by the source

29 Jun 2021, 21:24 UTC

Last modified by the source

9 Feb 2023, 17:46 UTC

Source last checked

26 Oct 2026, 14:55 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-9cx9-x2gp-9qvh

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# Patch Next advisory brief: CVE-2020-15111

Advisory: CRLF vulnerability in Fiber
IDs: CVE-2020-15111, GHSA-9cx9-x2gp-9qvh
Record: https://patchnext.com/advisories/cve-2020-15111 (revision 1, source checked 26 Oct 2026, 14:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/gofiber/fiber 1.12.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gofiber/fiber: affected < 1.12.6; fixed in 1.12.6

## Suggested inspection (read-only)
- Go github.com/gofiber/fiber: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/gofiber/fiber.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-9cx9-x2gp-9qvh (GitHub-reviewed advisory GHSA-9cx9-x2gp-9qvh lists affected ranges: Go github.com/gofiber/fiber >=0 <1.12.6)

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