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CVE-2021-21335

29
FAUCET Score

CVE-2021-21335 describes a critical authentication bypass vulnerability in the SPNEGO HTTP Authentication Module for nginx (spnego-http-auth-nginx-module) prior to version 1.1.1. An attacker can exploit this flaw by using a malformed username to bypass basic authentication, impacting users who have enabled this feature. With a CVSS score of 9.8 (CRITICAL), this vulnerability is easily exploitable over the network with no user interaction, leading to potential full compromise of confidentiality, integrity, and availability. While no active exploitation, public exploit code, or significant community discussion has been observed, immediate patching to version 1.1.1 or disabling basic authentication is recommended.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.1.1CPE matchmatch criteria
cpe:2.3:a:spnego_http_authentication_module_project:spnego_http_authentication_module:*:*:*:*:*:nginx:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.66%
Probability of exploitation in next 30 days
EPSS Percentile
74.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0166 is in the 62nd percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / stnoonan/spnego-http-auth-nginx-module/commit/a06f9efca373e25328b1c53639a48decd0854570
PatchThird Party Advisory
github.com / stnoonan/spnego-http-auth-nginx-module/releases/tag/v1.1.1
Third Party Advisory
github.com / stnoonan/spnego-http-auth-nginx-module/security/advisories/GHSA-ww8q-72rx-hc54
PatchThird Party Advisory