Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

• CVE-2026-91973: 0.67% estimated exploitation activity in the next 30 days; percentile 52.13 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The /dav, /.well-known, and /feeds groups are registered on the root Echo instance with only BasicAuth and no rate limiter. CalDAV BasicAuth accepts the plain account password, so password guessing over /dav is unbounded and never returns 429, while /api/v1/login is throttled from the tenth attempt. The only anti-brute-force control on the instance is therefore bypassable. Details pkg/routes/routes.go (~lines 238-249) registers /.well-known, /dav, and /feeds with middleware.BasicAuth(...) and nothing else; registerCalDavRoutes adds no limiter. pkg/routes/caldav/auth.go (~lines 88-93) falls through to user.CheckUserCredentials with the plain account password when no CalDAV token matches. In contrast, /register, /login, etc. are wrapped by unauthRateLimit() — an unconditional 10/min/IP pre-auth floor that ignores ratelimit.enabled (default false). TOTP-enabled accounts and bot users are correctly refused, so this targets password-only accounts. PoC (verified at runtime against…

Published by the source

9 Oct 2026, 20:52 UTC

Last modified by the source

19 Oct 2026, 21:31 UTC

Source last checked

26 Oct 2026, 15:32 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m469-88xx-8rx2

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6737

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m469-88xx-8rx2

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# Patch Next advisory brief: CVE-2026-91973

Advisory: Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords
IDs: CVE-2026-91973, GHSA-m469-88xx-8rx2
Record: https://patchnext.com/advisories/cve-2026-91973 (revision 3, source checked 26 Oct 2026, 15:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: code.vikunja.io/api 2.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected <= 2.5.0; fixed in 2.6.0

## Suggested inspection (read-only)
- Go code.vikunja.io/api: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on code.vikunja.io/api.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6737 (OSV record GO-2026-6737 lists affected ranges: Go code.vikunja.io/api >=0)
- Verified: https://osv.dev/vulnerability/GHSA-m469-88xx-8rx2 (OSV record GHSA-m469-88xx-8rx2 lists affected ranges: Go code.vikunja.io/api >=0 <2.6.0 (fixed))
- Verified: https://github.com/advisories/GHSA-m469-88xx-8rx2 (GitHub-reviewed advisory GHSA-m469-88xx-8rx2 lists affected ranges: Go code.vikunja.io/api >=0 <=2.5.0)

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