CVE-2026-21881: Kanboard is project management software focused on Kanban methodology

Q: How do I fix CVE-2026-21881?

kanboard: upgrade to 1.2.49. Exact commands for each OS are on this page.

Q: Is CVE-2026-21881 being exploited?

CVE-2026-21881 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-21881 affect?

CVE-2026-21881 affects kanboard. Severity is critical (CVSS 9.1). 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 auth

Q: How urgent is CVE-2026-21881?

Priority 52/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.1REMOTEUPGRADE

CVE-2026-21881 is a critical-severity flaw (CVSS 9.1) affecting kanboard. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-287
Published	2026-01-08
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: kanboard

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-01-08 02:15 UTCPublished CVE record published
2026-06-17 10:19 UTCUpdated Record last modified

kanboard kanboard UPGRADE

Affected: < 1.2.49

Fixed in: 1.2.49

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy kanboard || rpm -q kanboard || kanboard --version

2. UPGRADE to 1.2.49 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade kanboard

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade kanboard

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-21881?

kanboard: upgrade to 1.2.49. Exact commands for each OS are on this page.

Is CVE-2026-21881 being exploited?

CVE-2026-21881 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-21881 affect?

CVE-2026-21881 affects kanboard. Severity is critical (CVSS 9.1). 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 auth

How urgent is CVE-2026-21881?

Priority 52/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-33058 MEDIUM 6.5 UPGRADE Kanboard is project management software focused on Kanban methodology
CVE-2026-29056 HIGH 8.8 UPGRADE Kanboard is project management software focused on Kanban methodology
CVE-2026-25924 HIGH 8.4 UPGRADE Kanboard is project management software focused on Kanban methodology
CVE-2026-25531 MEDIUM 4.3 UPGRADE Kanboard is project management software focused on Kanban methodology
CVE-2026-25530 MEDIUM 4.3 UPGRADE Kanboard is project management software focused on Kanban methodology

References

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