# CVE-2026-76216: Vikunja link-share principal-type confusion in permission checks

Source: https://junglewise.ai/threats/cve-2026-76216-vikunja-link-share-principal-type-confusion-enables-cross-account  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-09. Updated: 2026-10-09  
License: CC BY 4.0 with a link back

CVE-2026-76216 · Severity: high · CVSS 7.5 · Published 2026-10-09

Vikunja is a task management and organization system. A bug in permission validation allows a guest with a public share link to be mistakenly treated as a specific user in certain contexts, enabling them to remove that user from teams, delete their bot accounts, and read team rosters without authorization.

Technologies: [code.vikunja.io/api (Go)](https://junglewise.ai/threats/technologies/code-vikunja-io-api), [Vikunja](https://junglewise.ai/threats/technologies/vikunja). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Vikunja](https://junglewise.ai/threats/vendors/vikunja).

## Quick answers

**Is CVE-2026-76216 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-76216 being exploited in the wild.

**How severe is CVE-2026-76216?** High severity, with a CVSS score of 7.5, published 9 October 2026.

**Which products and versions are affected?** code.vikunja.io/api (Go) <= 2.4.0, SEMVER:introduced=0, SEMVER:introduced=0,last_affected=2.4.0; Vikunja <= 2.4.0.

**Is there a fix for CVE-2026-76216?** No fixed version is recorded yet. Disable link sharing via configuration (`ServiceEnableLinkSharing.setDefault(false)`) until upgrading, or apply the suggested fix to add principal-type guards to the three vulnerable permission checks: `TeamMember.CanDelete`, `BotUser.isOwner`, and `Team.CanRead`.</anigation>
</invoke> If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-76216 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-76216?** Check whether you run code.vikunja.io/api (Go) or Vikunja at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix


Disable link sharing via configuration (`ServiceEnableLinkSharing.setDefault(false)`) until upgrading, or apply the suggested fix to add principal-type guards to the three vulnerable permission checks: `TeamMember.CanDelete`, `BotUser.isOwner`, and `Team.CanRead`.</anigation>
</invoke>

## Technical details

The `web.Auth` interface is implemented by both user principals and link-sharing principals, but three permission checks—`TeamMember.CanDelete`, `BotUser.isOwner`, and `Team.CanRead`—compare the raw positive `LinkSharing.GetID()` directly against user IDs without the principal-type guard that exists in sibling methods. When a link-share ID N numerically matches a user's ID N, the link-share is treated as that user, bypassing authorization. The vulnerability requires default-enabled link sharing and ID collision based on autoincrement sequencing.

## Affected products

- Vikunja Vikunja <= 2.4.0

## Identifiers

- CVE-2026-76216
- GHSA-32r8-5843-4qw2
- GO-2026-6711

## Timeline

- 2026-10-09: disclosed: GHSA-32r8-5843-4qw2 published

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