Vikunja: Denial of service via decompression bomb in the data import

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-2026-91979: 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.

Summary Vikunja lets you export your data as a zip and import it back. The import doesn't limit how large the archive expands to, how many files it contains, or how much storage one user can consume, and it appears to hold the whole archive in memory while processing it. Because the archive is compressed, a ~20 MB upload made of highly compressible content expands to tens of gigabytes once imported. A single crafted upload is enough to exhaust the server's memory or fill its disk and knock the whole instance offline. It can be repeated or run in parallel, since nothing stops a user from starting several imports at once. Details The import accepts an archive in the same layout the built-in export produces: a manifest describing projects and tasks, plus the attachment files those tasks reference. Each individual file inside the archive is size-checked, but there's no ceiling on the total uncompressed size or on the number of files, and there's no per-user storage quota anywhere. On top…

Published by the source

9 Oct 2026, 20:52 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-w7jp-mf2v-8342

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-2026-6756

4. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w7jp-mf2v-8342

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# Patch Next advisory brief: CVE-2026-91979

Advisory: Vikunja: Denial of service via decompression bomb in the data import
IDs: CVE-2026-91979, GHSA-w7jp-mf2v-8342
Record: https://patchnext.com/advisories/cve-2026-91979 (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; 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-2026-6756 (OSV record GO-2026-6756 lists affected ranges: Go code.vikunja.io/api >=0)
- Verified: https://osv.dev/vulnerability/GHSA-w7jp-mf2v-8342 (OSV record GHSA-w7jp-mf2v-8342 lists affected ranges: Go code.vikunja.io/api >=0 <2.6.0 (fixed))
- Verified: https://github.com/advisories/GHSA-w7jp-mf2v-8342 (GitHub-reviewed advisory GHSA-w7jp-mf2v-8342 lists affected ranges: Go code.vikunja.io/api >=0 <=2.5.0)

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