CVE-2026-91973 HIGH

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

Vendor Go-Vikunja

Product vikunja

Weakness CWE-307 · Brute force

Published September 15, 2026

Last update September 15, 2026

View on NVD All CVEs

CVSS base score

8.7/10

Attack vector Network

Attack complexity Low

Privileges required None

User interaction None

Confidentiality —

Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

September 15, 2026 CVE published

September 15, 2026 Record updated

External resources

03References

NVD — National Vulnerability Database https://nvd.nist.gov/vuln/detail/CVE-2026-91973 CWE — Common Weakness Enumeration https://cwe.mitre.org/data/definitions/307.html AskarLabs — CWE-307 write-up Improper Restriction of Excessive Authentication Attempts

Related vulnerabilities

04Related CVE

CVE-2023-44235 WordPress WP Captcha plugin <= 2.0.0 - Captcha Bypass vulnerability CVE-2025-10658 SupportCandy – Helpdesk & Customer Support Ticket System <= 3.3.7 - Authentication Bypass to Support Session Takeover CVE-2025-22645 WordPress Real Estate Manager plugin <= 7.3 - Captcha Bypass Vulnerability vulnerability CVE-2025-3129 Access code - Moderately critical - Access bypass - SA-CONTRIB-2025-028 CVE-2023-35039 WordPress Password Reset with Code for WordPress REST API Plugin <= 0.0.15 is vulnerable to Broken Authentication