CVE-2026-91973: Brute Force (CVSS 7.5)

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.

Is your site exposed to CVE-2026-91973?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

7.5

HIGH

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

EPSS — Exploit Prediction

0.0061

Probability of exploitation

0.48%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-307 CWE-307

References

Other References

https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2 https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2

Frequently Asked Questions

What is CVE-2026-91973? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-91973? +

CVE-2026-91973 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0061, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-91973? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-2911

Unauthorised access to the call forwarding service system in MeetMe products in versions prior to 2024-09 allows an attacker to …

CVE-2025-24806

Authelia is an open-source authentication and authorization server providing two-factor authentication and single sign-on (SSO) for applications via a web …

CVE-2025-1714

Lack of Rate Limiting in Sign-up workflow in Perforce Gliffy prior to version 4.14.0-7 on Gliffy online allows attacker to …

CVE-2025-0417

Lack of protection against brute force attacks in Valmet DNA visualization in DNA Operate. The possibility to make an arbitrary …

CVE-2025-42600

This vulnerability exists in Meon KYC solutions due to missing restrictions on the number of incorrect One-Time Password (OTP) attempts …

CVE-2025-6029

Use of fixed learning codes, one code to lock the car and the other code to unlock it, the Key …

CVE-2026-91973