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GHSA-94xm-jj8x-3cr4 CVE-2026-33668 GO-2026-4849

Vikunja Allows Disabled/Locked User Accounts to Authenticate via API Tokens, CalDAV, and OpenID Connect

High Go
Severity
0.0 / 10
High · CVSS 4.0
Exploit chance (EPSS)
0.46%
Chance of exploitation in the next 30 days. Higher than 39.97% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-285 Improper Authorization
Fix
2.2.1
Upgrade code.vikunja.io/api to this version or later

Description

Summary

When a user account is disabled or locked, the status check is only enforced on the local login and JWT token refresh paths. Three other authentication paths — API tokens, CalDAV basic auth, and OpenID Connect — do not verify user status, allowing disabled or locked users to continue accessing the API and syncing data.

Details

User status (StatusDisabled, StatusAccountLocked) is checked in only two places:

  1. Local/LDAP login (pkg/routes/api/v1/login.go:74) — prevents issuing new JWTs
  2. JWT token refresh (pkg/routes/api/v1/login.go:247) — prevents refreshing expired JWTs

Three other authentication paths fetch the user from the database via GetUserByID but never inspect the returned user's status:

1. API Token Authentication (pkg/routes/api_tokens.go:76-103)

API tokens are long-lived (up to years) and have no refresh cycle. A disabled user's API tokens remain fully functional until they expire naturally.

2. CalDAV Basic Auth (pkg/routes/caldav/auth.go)

The CalDAV basic auth handler validates credentials but does not check user status before granting access. A disabled user with valid credentials or a CalDAV token can continue syncing calendars and tasks.

3. OpenID Connect Callback (pkg/modules/auth/openid/openid.go)

The OIDC callback issues a fresh JWT token after validating the identity provider's response but does not check whether the Vikunja user account is disabled. If the user's identity provider session is still active, they receive a valid JWT despite being disabled in Vikunja.

Impact

An administrator who disables a user account expects that user to be immediately locked out. In practice:

  • API tokens: The user retains full API access for the remaining lifetime of any issued API tokens — potentially months or years.
  • CalDAV: The user can continue reading and writing tasks/events via any CalDAV client.
  • OIDC: The user can obtain a fresh, fully valid JWT by re-authenticating through their identity provider, completely bypassing the account disable.

Proof of Concept

  1. Create a user and generate an API token.
  2. Disable the user account via the admin API or CLI.
  3. Make an API request using the API token: 
    curl -H "Authorization: Bearer tk_<token>" https://vikunja.example/api/v1/user
  4. The request succeeds with a 200 response despite the account being disabled.

Affected versions

Go

PackageVulnerableFixed in
code.vikunja.io/api
>= 0.18.0, < 2.2.1
2.2.1
code.vikunja.io/api
>= 0.18.0
 No fix yet

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

code.vikunja.io/api Go → 2.2.1

go
go get code.vikunja.io/api@v2.2.1 && go mod tidy

Severity breakdown

CVSS 4.0 0.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Attack vector
Network
Attack complexity
Low
Attack requirements
None
Privileges required
Low
User interaction
None
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
High
Availability (vulnerable system)
None
Confidentiality (subsequent systems)
None
Integrity (subsequent systems)
None
Availability (subsequent systems)
None

CVSS 3.1 8.1

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

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Weakness

CWE-285: Improper Authorization

The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.

How to prevent it
  • Architecture and Design: Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
  • Architecture and Design: Ensure that you perform access control checks related to your business logic. These checks may be different than the access control checks that you apply to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.
  • Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
  • Architecture and Design: For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page. One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
  • System Configuration, Installation: Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-m687-p538-r5hp
Vikunja: Permissive Cross-domain Security Policy trusts every localhost origin which should not be trusted
Medium Also affects code.vikunja.io/api
GHSA-fmmf-xq98-g327
Vikunja: Write-level project members can delete admin-tier link shares through an unloaded permission check
Medium Also affects code.vikunja.io/api
GHSA-pjr3-86v4-5p7w
Vikunja: Explicit lower-permission share on a sub-project is silently overridden by an inherited parent permission (broken access control / privilege-management regression in v2.6.0)
Medium Also affects code.vikunja.io/api
GHSA-hjx8-qv73-f7cm
Vikunja: Webhooks and link shares survive every revocation path, so a removed collaborator keeps a live feed
High Also affects code.vikunja.io/api
GHSA-fprf-r6rv-xg99
Vikunja: Saved filter creation with an empty filter string recalculates task positions across all tenants
Medium Also affects code.vikunja.io/api
GHSA-4hv6-xc92-j86g
Vikunja: WebSocket authentication ignores server-side session state, so revoked sessions keep receiving live pushes
High Also affects code.vikunja.io/api
GHSA-w2ch-4xgr-22ww
Vikunja: Task relation deletion does not check read access to the other task, allowing cross-project relation removal
Low Also affects code.vikunja.io/api
GHSA-8wvg-r2j4-3737
Vikunja: Assignee email addresses disclosed to read-only project members via the task assignees endpoint
Medium Also affects code.vikunja.io/api
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