Is CVE-2026-21881 in the CISA KEV catalog?

No. CVE-2026-21881 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-21881?

CVE-2026-21881 has a CVSS v3 base score of 9.1 (CRITICAL).

What is the EPSS score for CVE-2026-21881?

CVE-2026-21881 has an EPSS score of 0.43% (34th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2026-21881

CRITICAL

9.1

CVSS v3

NVD

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.

CWE-287Improper Authentication

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Exploit Intelligence

0.43%probability of exploitation in 30 days

34thpercentile

Low risk: more likely to be exploited than 34% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-01-20.