CVE-2021-32637

Authentication bypassed with malformed request URI

CRITICAL
10
CVSS Score
Published: May 28, 2021 at 05:00 PM UTC
Updated: June 17, 2026 at 03:53 AM UTC
1 product affected across 1 vendorAuthelia

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Severity
CRITICAL10
Exploit prediction
EPSS 2%

Description

Authelia is a a single sign-on multi-factor portal for web apps. This affects uses who are using nginx ngx_http_auth_request_module with Authelia, it allows a malicious individual who crafts a malformed HTTP request to bypass the authentication mechanism. It additionally could theoretically affect other proxy servers, but all of the ones we officially support except nginx do not allow malformed URI paths. The problem is rectified entirely in v4.29.3. As this patch is relatively straightforward we can back port this to any version upon request. Alternatively we are supplying a git patch to 4.25.1 which should be relatively straightforward to apply to any version, the git patches for specific versions can be found in the references. The most relevant workaround is upgrading. You can also add a block which fails requests that contains a malformed URI in the internal location block.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 4.29.34.0.0 ≤ v < 4.25.14.26.0 ≤ v < 4.29.3
Affected range stops below 4.25.1, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.29.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

CVSS

10CRITICALGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-287

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