High severity · published Sep 15, 2026
CVE-2026-91973
Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth
7.5
CVSS
0.7%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.7% · higher than 52% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
VI
vikunja · go-vikunja
before 2.6.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-91973
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-91973
github.com
https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2
www.vulncheck.com
https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth
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