CVE-2021-21335

Name: CVE-2021-21335
Creator: NVD / NIST
Published: 2021-03-08T21:15:16.573+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.66%

Last modified Jun 17, 2026

CVE-2021-21335 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. In the SPNEGO HTTP Authentication Module for nginx (spnego-http-auth-nginx-module) before version 1.1.1 basic Authentication can be bypassed using a malformed username. This affects users of spnego-http-auth-nginx-module that have enabled basic authentication. EPSS estimates a 1.66% chance of exploitation in the next 30 days.

Description

In the SPNEGO HTTP Authentication Module for nginx (spnego-http-auth-nginx-module) before version 1.1.1 basic Authentication can be bypassed using a malformed username. This affects users of spnego-http-auth-nginx-module that have enabled basic authentication. This is fixed in version 1.1.1 of spnego-http-auth-nginx-module. As a workaround, one may disable basic authentication.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

1.66%

73.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-287

Affected Software

Vendor	Product	Versions
Spnego Http Authentication Module Project	Spnego Http Authentication Module	< 1.1.1

References

https://github.com/stnoonan/spnego-http-auth-nginx-module/commit/a06f9efca373e25328b1c53639a48decd0854570Patch, Third Party Advisory
https://github.com/stnoonan/spnego-http-auth-nginx-module/releases/tag/v1.1.1Third Party Advisory
https://github.com/stnoonan/spnego-http-auth-nginx-module/security/advisories/GHSA-ww8q-72rx-hc54Patch, Third Party Advisory
https://github.com/stnoonan/spnego-http-auth-nginx-module/commit/a06f9efca373e25328b1c53639a48decd0854570Patch, Third Party Advisory
https://github.com/stnoonan/spnego-http-auth-nginx-module/releases/tag/v1.1.1Third Party Advisory
https://github.com/stnoonan/spnego-http-auth-nginx-module/security/advisories/GHSA-ww8q-72rx-hc54Patch, Third Party Advisory

Timeline

Published: Mar 8, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21335?

How severe is CVE-2021-21335?

CVE-2021-21335 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.66% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21335?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21335?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST