CVE-2026-91973 json
Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth
published 2026-09-15 54 d ago modified 2026-10-19 20 d ago also GHSA-m469-88xx-8rx2 , GO-2026-6737 , EUVD-2026-78649
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.7%
- EPSS 0.7% chance of exploitation in 30 days, percentile 52%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- go code.vikunja.io/api 2.6.0
- go-vikunja vikunja 2.6.0
- github.com/go-vikunja/vikunja#3688 pull request
- github.com/go-vikunja/vikunja/releases/tag/v2.6.0 release
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 54 d ago
Exploit prediction
0.67% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.7 | 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 |
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
| CNA | 4.0 | 8.7 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | code.vikunja.io/api | <2.6.0 all versions |
2.6.0 |
Affected products
- go-vikunja vikunja
Classification
- Weakness
-
- CWE-307 Improper Restriction of Excessive Authentication Attempts
References
-
github.com
/go-vikunja/vikunja/pull/3688
web
-
github.com
/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2
vendor-advisory, exploit, web, advisory
-
vulncheck.com
/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth
third-party-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-91973
advisory
-
github.com
/go-vikunja/vikunja
package
-
github.com
/go-vikunja/vikunja/releases/tag/v2.6.0
web
Sources
- CVE List CVE-2026-91973
- GitHub Advisory GHSA-m469-88xx-8rx2
- NVD CVE-2026-91973
- OSV GO-2026-6737
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.