kanboard up to 1.2.48 REVERSE_PROXY_AUTH improper authentication

Summaryinfo

A vulnerability classified as critical was found in kanboard up to 1.2.48. This affects an unknown function. Executing a manipulation of the argument REVERSE_PROXY_AUTH can lead to improper authentication. This vulnerability appears as CVE-2026-21881. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in kanboard up to 1.2.48. It has been declared as critical. This vulnerability affects an unknown function. The manipulation of the argument REVERSE_PROXY_AUTH with an unknown input leads to a improper authentication vulnerability. The CWE definition for the vulnerability is CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Kanboard is project management software focused on Kanban methodology. Versions 1.2.48 and below is vulnerable to a critical authentication bypass when REVERSE_PROXY_AUTH is enabled. The application blindly trusts HTTP headers for user authentication without verifying the request originated from a trusted reverse proxy. An attacker can impersonate any user, including administrators, by simply sending a spoofed HTTP header. This issue is fixed in version 1.2.49.

The advisory is available at github.com. This vulnerability was named CVE-2026-21881 since 01/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 282469 (Linux Distros Unpatched Vulnerability : CVE-2026-21881), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.2.49 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 7af6143e2ad25b5c15549cca8af4341c7ac4e2fc is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (282469). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Forum Software

Name

• kanboard

Version

• 1.2.0
• 1.2.1
• 1.2.2
• 1.2.3
• 1.2.4
• 1.2.5
• 1.2.6
• 1.2.7
• 1.2.8
• 1.2.9
• 1.2.10
• 1.2.11
• 1.2.12
• 1.2.13
• 1.2.14
• 1.2.15
• 1.2.16
• 1.2.17
• 1.2.18
• 1.2.19
• 1.2.20
• 1.2.21
• 1.2.22
• 1.2.23
• 1.2.24
• 1.2.25
• 1.2.26
• 1.2.27
• 1.2.28
• 1.2.29
• 1.2.30
• 1.2.31
• 1.2.32
• 1.2.33
• 1.2.34
• 1.2.35
• 1.2.36
• 1.2.37
• 1.2.38
• 1.2.39
• 1.2.40
• 1.2.41
• 1.2.42
• 1.2.43
• 1.2.44
• 1.2.45
• 1.2.46
• 1.2.47
• 1.2.48

License

• open-source

Website

• Product: https://github.com/kanboard/kanboard/

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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