CVE-2026-33313

An authenticated user can read any task comment by ID, regardless of whether they have access to the task the comment belongs to, by substituting the task ID in the API URL with a task they do have access to.

Details

The GET /api/v1/tasks/{taskID}/comments/{commentID} endpoint performs an authorization check against the task ID provided in the URL path, then loads the comment by its own ID without verifying it belongs to that task.

Root Cause

In pkg/models/task_comment_permissions.go, CanRead constructs a Task using the TaskID from the URL and checks Task.CanRead:

func (tc *TaskComment) CanRead(s *xorm.Session, a web.Auth) (bool, int, error) {
    t := Task{ID: tc.TaskID}
    return t.CanRead(s, a)
}

In pkg/models/task_comments.go, getTaskCommentSimple loads the comment by ID only, with NoAutoCondition() explicitly disabling XORM's implicit struct-field filtering:

func getTaskCommentSimple(s *xorm.Session, tc *TaskComment) error {
    exists, err := s.
        Where("id = ?", tc.ID).
        NoAutoCondition().
        Get(tc)
    // ...
}

The generic web handler (pkg/web/handler/read_one.go) calls CanRead before ReadOne, so the permission check passes against the attacker-controlled task ID, and then ReadOne returns the comment from a completely different task.

Attack Scenario

1. Attacker is authenticated and has read access to any task (task ID A), e.g. their own task.
2. Attacker guesses or enumerates a comment ID (C) belonging to a task in another user's private project.
3. Attacker requests: GET /api/v1/tasks/A/comments/C
4. Authorization passes because the attacker can read task A.
5. The comment C is loaded by ID only and returned, leaking its contents and author.

Credit

This vulnerability was found using GitHub Security Lab Taskflows.

Kodem intelligence

1. What is CVE-2026-33313? CVE-2026-33313 is a medium-severity security vulnerability in code.vikunja.io/api (go), affecting versions <= 2.1.0. No fixed version is listed yet.
2. Which versions of code.vikunja.io/api are affected by CVE-2026-33313? code.vikunja.io/api (go) versions <= 2.1.0 is affected.
3. Is there a fix for CVE-2026-33313? No fixed version is listed for CVE-2026-33313 yet. Monitor the advisory for updates and apply mitigations in the interim.
4. Is CVE-2026-33313 exploitable, and should I be worried? Whether CVE-2026-33313 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-33313 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.