vulnerability / NVI-00011934 / Revision 4
Vikunja: Link-share principal ID collision allows cross-account API token issuance and management
GitHub lists this reviewed advisory for code.vikunja.io/api. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
8.1 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
8.1 HIGH (3.1)
disclosure@vulncheck.com severity; no combined Null risk score.
8.6 HIGH (4.0)
disclosure@vulncheck.com severity; no combined Null risk score.
0.464%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.40311. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
code.vikunja.io/api
source listed>= 0.22.0, <= 2.3.0
Executive Summary Vikunja accepts both regular-user JSON Web Tokens (JWTs) and link-share JWTs through its generic authenticated API route group. A link-share JWT resolves to a `models.LinkSharing` principal whose `GetID()` method returns the numeric `link_shares.id`. The API-token management model then treats that generic numeric value as a `users.id` when it creates, lists, and deletes API tokens. Because `users.id` and `link_shares.id` are independent positive sequences, a link share whose ID equals another user's ID is treated as that user by `/api/v1/tokens`. An ordinary authenticated attacker can obtain a target's numeric user ID through authenticated user search and create link shares on an attacker-writable project until the link-share sequence reaches that value. The colliding link-share principal can then list the target's API-token metadata, issue a new API token owned by the target, and delete target-owned API tokens. The newly issued token operates with attacker-selected valid API scopes under the target user's existing permissions. I reviewed the vulnerable `v2.3.0` source, the introducing commit, the stable tag history, and the inspected main revision directly. I
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-vvcv-vpph-h844 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-68581 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
- CVE-2026-68581 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 4 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 3 ·
Source facts changed; compare the preserved prior revision.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.