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CVE-2026-21881— Kanboard is Vulnerable to Reverse Proxy Authentication Bypass

Quick assessment

Affected
kanboard kanboard
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Kanboard是Kanboard开源的一套开源的可视化任务板软件。该软件能够根据业务定制面板。 Kanboard 1.2.48及之前版本存在安全漏洞，该漏洞源于启用REVERSE_PROXY_AUTH时存在认证绕过，可能导致攻击者冒充任何用户。

CVSS 9.1 · Critical EPSS 0.49% · P40

Possible ATT&CK Techniques 1 AI

T1110 · Brute Force
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I. Basic Information for CVE-2026-21881

Vulnerability Information
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Vulnerability Title
Kanboard is Vulnerable to Reverse Proxy Authentication Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Kanboard 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Kanboard是Kanboard开源的一套开源的可视化任务板软件。该软件能够根据业务定制面板。 Kanboard 1.2.48及之前版本存在安全漏洞，该漏洞源于启用REVERSE_PROXY_AUTH时存在认证绕过，可能导致攻击者冒充任何用户。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
kanboard kanboard < 1.2.49 -

II. Public POCs for CVE-2026-21881

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 6392 chars
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III. Intelligence Information for CVE-2026-21881

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Patches & Fixes for CVE-2026-21881 (1)

Vendor Advisories for CVE-2026-21881 (1)

Other References for CVE-2026-21881 (1)

Same Patch Batch · kanboard · 2026-01-08 · 3 CVEs total

CVE-2026-21880 5.3 MEDIUM Kanboard LDAP Injection Vulnerability can Lead to User Enumeration and Information Disclos
CVE-2026-21879 4.7 MEDIUM Kanboard vulnerable to Open Redirect via protocol-relative URLs

IV. Related Vulnerabilities

Same product: kanboard
Same vendor: kanboard
Same weakness: CWE-287

V. Comments for CVE-2026-21881

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