CVE-2020-15111

CRLF vulnerability in Fiber

package main

import "github.com/gofiber/fiber"

const badFileName = "another secret document.pdf\"\r\nLocation: google.com\r\nAuthorization: \"example_of_session_fixation"

func splitTheResponse(c *fiber.Ctx) {
	c.Attachment(badFileName)
}

func main() {
	app := fiber.New()
	app.Get("/attack", splitTheResponse)
	app.Listen("127.0.0.1:8080")
}

HTTP/1.1 200 OK
Date: Fri, 10 Jul 2020 19:47:04 GMT
Content-Type: application/octet-stream
Content-Length: 0
Content-Disposition: attachment; filename="another secret document.pdf"
Location: google.com
Authorization: "example_of_session_fixation"

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.

CVE-2020-15111 has a CVSS score of 4.2 (Medium). The vector is network-reachable, no privileges required, and user interaction required. 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 (1.12.6); upgrading removes the vulnerable code path.

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This issue has been patched in v1.12.6 with commit 579 escaping the filename by default.

1. What is CVE-2020-15111? CVE-2020-15111 is a medium-severity security vulnerability in github.com/gofiber/fiber (go), affecting versions < 1.12.6. It is fixed in 1.12.6.
2. How severe is CVE-2020-15111? CVE-2020-15111 has a CVSS score of 4.2 (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 versions of github.com/gofiber/fiber are affected by CVE-2020-15111? github.com/gofiber/fiber (go) versions < 1.12.6 is affected.
4. Is there a fix for CVE-2020-15111? Yes. CVE-2020-15111 is fixed in 1.12.6. Upgrade to this version or later.
5. Is CVE-2020-15111 exploitable, and should I be worried? Whether CVE-2020-15111 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-2020-15111 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-2020-15111? Upgrade github.com/gofiber/fiber to 1.12.6 or later.

Other vulnerabilities in github.com/gofiber/fiber