---
id: CVE-2026-91973
title: >-
  Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV
  BasicAuth endpoints that lack rate limiting protection
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…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-307
vendor: go-vikunja
product: vikunja
affected:
  - vikunja < 2.6.0
published: '2026-09-15'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T20:16:09.343'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-91973'
references:
  - url: >-
      https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-15T15:53:33.159049Z'
ingestedAt: '2026-09-15T15:39:12.913Z'
epss: 0.00609
epssPercentile: 0.47848
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.