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High, CVSS 7.5amended

Vikunja: Link-share principal-type confusion enables cross-account team removal, bot takeover, and roster disclosure

CVE-2026-76216GHSA-32r8-5843-4qw2

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (code.vikunja.io/api 2.5.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2026-76216: 0.36% estimated exploitation activity in the next 30 days; percentile 30.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Vikunja's `web.Auth` interface (`pkg/web/web.go`, single method `GetID() int64`) is satisfied by BOTH `*user.User` and `*models.LinkSharing`. A link-share's `GetID()` returns the raw positive `share.ID` (`pkg/models/link_sharing.go:83-85`), which lives in the same positive autoincrement ID space as `users.id`. The safe negated form `getUserID() = share.ID * -1` (`link_sharing.go:126-128`) exists but is NOT used at three permission sinks. As a result, a link-share principal with id `N` — which should have zero authority over teams or bot users — is treated as the *user* whose `users.id == N` at three permission checks that lack the `a.(*LinkSharing)` guard their sibling methods have. This is the same principal-type-confusion class as CVE-2026-68581 (GHSA-vvcv-vpph-h844), but at three code paths that advisory/fix never touched.

Root Cause `web.Auth` is a one-method interface (`GetID() int64`). `*LinkSharing.GetID()` returns the raw positive share id. Three permission…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 5 · amended ·

    Amended from osv record GHSA-32r8-5843-4qw2

  2. Revision 4 · amended ·

    Amended from ghsa record GHSA-32r8-5843-4qw2

  3. Revision 3 · amended ·

    Amended from ghsa record GHSA-32r8-5843-4qw2

  4. Revision 2 · amended ·

    Amended from osv record GO-2026-6711

  5. Revision 1 · created ·

    Published from osv record GHSA-32r8-5843-4qw2

Agent brief

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# Patch Next advisory brief: CVE-2026-76216

Advisory: Vikunja: Link-share principal-type confusion enables cross-account team removal, bot takeover, and roster disclosure
IDs: CVE-2026-76216, GHSA-32r8-5843-4qw2
Record: https://patchnext.com/advisories/cve-2026-76216 (revision 5, source checked 28 Oct 2026, 06:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
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 2.5.0. A vendor fix does not mean a deployment is fixed.

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

## 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-2026-6711 (OSV record GO-2026-6711 lists affected ranges: Go code.vikunja.io/api >=0)
- Verified: https://osv.dev/vulnerability/GHSA-32r8-5843-4qw2 (OSV record GHSA-32r8-5843-4qw2 lists affected ranges: Go code.vikunja.io/api >=0 <=2.4.0)
- Verified: https://osv.dev/vulnerability/GHSA-32r8-5843-4qw2 (OSV record GHSA-32r8-5843-4qw2 lists affected ranges: Go code.vikunja.io/api >=0 <2.5.0 (fixed))
- Verified: https://github.com/advisories/GHSA-32r8-5843-4qw2 (GitHub-reviewed advisory GHSA-32r8-5843-4qw2 lists affected ranges: Go code.vikunja.io/api >=0 <=2.4.0)
- Verified: https://github.com/advisories/GHSA-32r8-5843-4qw2 (GitHub-reviewed advisory GHSA-32r8-5843-4qw2 lists affected ranges: Go code.vikunja.io/api >=0 <2.5.0)

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