HOMEVULNERABILITIESCVE-2021-21335
CRITICAL

CVE-2021-21335

CWE-287Published: March 8, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-21335 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

From a weakness classification perspective (CWE-287): Authentication bypass vulnerabilities allow attackers to access protected resources without valid credentials.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

spnego_http_authentication_module_project1 product(s)
spnego http authentication module
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
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Official Patches & Advisories

PATCHhttps://github.com/stnoonan/spnego-http-auth-nginx-module/commit/a06f9efca373e25328b1c53639a48decd0854570
PATCHhttps://github.com/stnoonan/spnego-http-auth-nginx-module/security/advisories/GHSA-ww8q-72rx-hc54
PATCHhttps://github.com/stnoonan/spnego-http-auth-nginx-module/commit/a06f9efca373e25328b1c53639a48decd0854570
PATCHhttps://github.com/stnoonan/spnego-http-auth-nginx-module/security/advisories/GHSA-ww8q-72rx-hc54
ADVISORYhttps://github.com/stnoonan/spnego-http-auth-nginx-module/releases/tag/v1.1.1
ADVISORYhttps://github.com/stnoonan/spnego-http-auth-nginx-module/releases/tag/v1.1.1

All References (6)

→
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

Quick Facts

CVE IDCVE-2021-21335
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessCWE-287
CISA KEVNo
Affected1 vendor(s)
PublishedMar 8, 2021

Related CVEs (CWE-287)

CVE-2015-0653
10.0
CVE-2015-0198
10.0
CVE-2015-2033
10.0
CVE-2014-2955
10.0
CVE-2014-2609
10.0
CVE-2017-3791
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-21335 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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