# CVE-2026-76216: Vikunja through 2.4.0 Principal-Type Confusion via LinkSharing

> Attackers with link-share JWTs can exploit ID collisions to remove team members, delete bots, or read rosters in Vikunja.

- **Severity:** High 7.7 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Aug 2026
- **Updated:** 20 Aug 2026
- **Also known as:** GHSA-32r8-5843-4qw2, GO-2026-6711

## What is CVE-2026-76216?

CVE-2026-76216 is a high-severity authentication bypass vulnerability in go-vikunja vikunja, published on 19 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Vikunja through 2.4.0 contains a principal-type confusion vulnerability where LinkSharing principals with id N are treated as user principals with users.id == N at three permission checks lacking type guards. Attackers with a link-share JWT can remove victims from teams, enumerate and delete victim bot users, or read team rosters by exploiting id collisions in the autoincrement space.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-76216?

3 open source packages ship an affected version, including code.vikunja.io/api.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `code.vikunja.io/api` | Go | All versions | None |
| `code.vikunja.io/api` | Go | All versions | 2.5.0 |
| `code.vikunja.io/api` | Go | All versions | 2.5.0 |

## How do I fix CVE-2026-76216?

Upgrade code.vikunja.io/api to 2.5.0 or later.

## Is CVE-2026-76216 being exploited?

There is no known exploitation of CVE-2026-76216 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76216 and fix it if it is affected.

What it is: CVE-2026-76216 is a high-severity authentication bypass vulnerability in go-vikunja vikunja, published on 19 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-76216 in the wild and no public exploit code.

Affected packages and fixed versions:
- code.vikunja.io/api (Go): affected all versions; no fix listed
- code.vikunja.io/api (Go): affected all versions; fixed in 2.5.0
- code.vikunja.io/api (Go): affected all versions; fixed in 2.5.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-76216/ (Markdown: https://insights.sbomify.com/CVE-2026-76216/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76216
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76216
- OSV: https://osv.dev/vulnerability/CVE-2026-76216

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-76216/
Summaries are generated and may contain mistakes; the official description above is the record.