Vikunja: Unbounded nested task-filter recursion permits API process termination

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-91968: 0.44% estimated exploitation activity in the next 30 days; percentile 37.89 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Unbounded nested task-filter recursion permits API process termination Summary Authenticated task-list routes accept a filter expression without a length or nesting-depth bound, preprocess it, parse it recursively through fexpr, and recursively convert the resulting expression tree. A syntactically valid deeply nested expression well below the HTTP request-size ceiling exhausts memory and kills the API process. Impact and affected scope - Type: Resource Exhaustion Recursive Parser - Affected component: GET /api/v2/projects/{project}/tasks?filter=<nested expression; Other authenticated task-collection entrypoints that share getTaskFiltersFromFilterString - Preconditions: A low-privileged authenticated user supplies thousands of balanced parentheses around a valid task predicate in the filter query parameter. - Verified revision: 349cd5adbcc831ef08b08e6c9c6d627603c39606 on 28 August 2026 - Affected release range: = 2.5.0; broader historical range not established and maintainer…

Published by the source

9 Oct 2026, 20:53 UTC

Last modified by the source

19 Oct 2026, 21:31 UTC

Source last checked

26 Oct 2026, 15:32 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xxc3-xpmc-vmvr

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6759

4. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xxc3-xpmc-vmvr

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# Patch Next advisory brief: CVE-2026-91968

Advisory: Vikunja: Unbounded nested task-filter recursion permits API process termination
IDs: CVE-2026-91968, GHSA-xxc3-xpmc-vmvr
Record: https://patchnext.com/advisories/cve-2026-91968 (revision 4, source checked 26 Oct 2026, 15:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: code.vikunja.io/api 2.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected >= 2.5.0, <= 2.5.0; fixed in 2.6.0

## Suggested inspection (read-only)
- Go code.vikunja.io/api: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on code.vikunja.io/api.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6759 (OSV record GO-2026-6759 lists affected ranges: Go code.vikunja.io/api >=0)
- Verified: https://osv.dev/vulnerability/GHSA-xxc3-xpmc-vmvr (OSV record GHSA-xxc3-xpmc-vmvr lists affected ranges: Go code.vikunja.io/api >=2.5.0 <2.6.0 (fixed))
- Verified: https://github.com/advisories/GHSA-xxc3-xpmc-vmvr (GitHub-reviewed advisory GHSA-xxc3-xpmc-vmvr lists affected ranges: Go code.vikunja.io/api >=2.5.0 <=2.5.0)

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