Vulnerability · Published Sep 15, 2026 · Assigned by VulnCheck

CVE-2026-91973Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth

High 7.5

In plain English

A high-severity security flaw in vikunja from go-vikunja. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.7%top 47.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV BasicAuth endpoints that lack rate limiting protection. Remote unauthenticated attackers can issue unbounded credential-guessing requests against /dav, /.well-known, and /feeds routes to bypass the instance's anti-brute-force controls and compromise password-only accounts.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Go	code.vikunja.io/api	2.6.0	GHSA-m469-88xx-8rx2
Go	code.vikunja.io/api	no fix listed	GO-2026-6737

Affected products (as reported)

Vendor	Product	Versions
go-vikunja	vikunja	0 – before 2.6.0

Weakness: CWE-307 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

GitHub Security Advisory (GHSA-m469-88xx-8rx2) vendor-advisory
VulnCheck Advisory: Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth third-party-advisory