Vikunja 0.13.0 before 2.7.0 Incorrect Authorization in Link Share Deletion

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Vikunja 0.13.0 before 2.7.0 contains an incorrect authorization vulnerability that allows project members with Write permission to delete admin-tier link shares because the delete permission check reads an unloaded share object. Attackers can send DELETE requests to the v1 or v2 projects shares endpoints with sequential share IDs to revoke admin links and invalidate existing share sessions.

Source published

17 Oct 2026 18:46:35 UTC

Source modified

21 Oct 2026 21:44:01 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 4.0 · 5.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS 3.1 · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

Vikunja 0.13.0 before 2.7.0 contains an incorrect authorization vulnerability that allows project members with Write permission to delete admin-tier link shares because the delete permission check reads an unloaded share object. Attackers can send DELETE requests to the v1 or v2 projects shares endpoints with sequential share IDs to revoke admin links and invalidate existing share sessions.

Source published

Oct 17, 2026, 6:46:35 PM (timezone not stated)

Source modified

Oct 21, 2026, 9:44:01 PM (timezone not stated)

Observed here

30 Oct 2026 01:56:47 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 4.0 · 5.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

Vikunja 0.13.0 before 2.7.0 contains an incorrect authorization vulnerability that allows project members with Write permission to delete admin-tier link shares because the delete permission check reads an unloaded share object. Attackers can send DELETE requests to the v1 or v2 projects shares endpoints with sequential share IDs to revoke admin links and invalidate existing share sessions.

Source published

17 Oct 2026 19:16:34 UTC

Source modified

21 Oct 2026 22:16:48 UTC

Observed here

25 Oct 2026 05:17:13 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 5.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Secondary · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

## Summary A project member with Write permission can delete an admin-tier link share on that project. The deletion authorization check reads the permission from an object populated only with URL IDs, rather than from the stored share. Its zero value is Read, so the check falls through to project Write permission instead of requiring Admin. ## Details Affected endpoints: - `DELETE /api/v1/projects/{project}/shares/{share}` - `DELETE /api/v2/projects/{project}/shares/{share}` Older v1 releases used `/lists/{list}/shares/{share}` before lists were renamed to projects. In `pkg/routes/api/v2/link_sharing.go:156`, the delete handler passes `&models.LinkSharing{ID: in.ID, ProjectID: in.ProjectID}` to `handler.DoDelete`. The v1 generic handler likewise binds the URL IDs without loading the stored share. `pkg/web/handler/core.go:185` calls `CanDelete` before `Delete`. `LinkSharing.CanDelete` delegates to `canDoLinkShare` in `pkg/models/link_sharing_permissions.go`. That helper loads the project but does not load the link share, then evaluates: ```go if share.Permission == PermissionAdmin { return l.IsAdmin(s, a) } return l.CanWrite(s, a) ``` On deletion, `share.Permission` is its Go zero value, `PermissionRead` (0), even when the stored share grants `PermissionAdmin` (2). A Write member therefore passes authorization. `LinkSharing.Delete` subsequently deletes by share ID and project ID without checking the stored permission. Create uses the requested permission and correctly rejects Write members creating admin shares. Share listing and by-ID reads are admin-gated in current main. There is no HTTP update route for link shares. Read-only members and link-share principals are rejected on deletion. ## Affected versions and verification The admin-tier check was introduced in commit `56dbb564eae83f2453efd1049f55e9d099b5d346`, first included in v0.13, without loading the stored share on deletion. The affected range established by this review is `>= 0.13.0, <= 2.6.0`; versions before v0.13 have not been assessed here. The v2 route was added in `b10768506`, first included in v2.4.0. The reporter states that both API versions were verified live against a local source build at `a881ac39eecd07575a5aede8e74727c28d5fd578` on September 7, 2026. Maintainer-side source review confirmed the mechanism in that commit, release v2.6.0, and upstream main at `a1a6ca48be142902f09fee62734310cb98a8c414`. The live proof of concept was not independently rerun during this triage. No patched version is available at draft creation. ## Impact A Write collaborator can revoke an admin-tier access link on a project they can already write to. New consumers can no longer authenticate with that link. In versions with database-backed link-share JWT validation, deleting the share also immediately invalidates its existing sessions; the reporter observed HTTP 404 for a new hash exchange and HTTP 401 for an existing share token. This is a bounded integrity and availability impact on external access to that project. It does not disclose data, grant Admin privileges, allow deletion of another project's shares, or permit the attacker to create a replacement admin share. The attacker must know or guess the numeric share ID; IDs are sequential. Severity: Medium. CWE-863: Incorrect Authorization. ## Proof of concept Use two regular accounts on an instance you control. Let `OWNER_TOKEN` and `WRITER_TOKEN` be their session tokens. Create a project as the owner, grant the second account Write permission (`permission: 1`), and create an admin-tier share as the owner (`permission: 2`). Let `PROJECT_ID` and `SHARE_ID` identify that project and share. First, verify that the Write member cannot create an admin-tier share: ```sh curl -i -X POST "$BASE/api/v2/projects/$PROJECT_ID/shares" \ -H "Authorization: Bearer $WRITER_TOKEN" \ -H 'Content-Type: application/json' \ -d '{"permission":2}' # Expected and reported: 403 ``` Delete the owner's admin-tier share as the same Write member: ```sh curl -i -X DELETE "$BASE/api/v2/projects/$PROJECT_ID/shares/$SHARE_ID" \ -H "Authorization: Bearer $WRITER_TOKEN" # Reported: 204; expected: 403 and the share remains intact ``` Recreate the admin-tier share as the owner and repeat with the v1 endpoint: ```sh curl -i -X DELETE "$BASE/api/v1/projects/$PROJECT_ID/shares/$SHARE_ID" \ -H "Authorization: Bearer $WRITER_TOKEN" # Reported: 200 with {"message":"Successfully deleted."}; expected: 403 ``` With the collaborator downgraded to Read, deletion returns 403. These positive and negative controls were reported as verified live by the reporter. ## Recommended fix For deletion, load the stored share scoped to both the requested share ID and project ID before authorizing. Require project Admin when the stored permission is Admin, and retain the intended Write rule for ordinary read/write shares. Preserve the existing cross-project constraint. Keep creation authorization based on the requested tier. If update support is added, check both the stored tier and the requested new tier so neither demotion nor promotion can bypass the admin check. Add regression coverage for a Write member being forbidden to delete an admin-tier share, an Admin being allowed, intended ordinary-share deletion, rejection of Read members and link-share principals, and mismatched project/share IDs. Cover both API versions. ## Related advisories - [GHSA-f95f-77jx-fcjc / CVE-2026-33700](https://github.com/go-vikunja/vikunja/security/advisories/GHSA-f95f-77jx-fcjc) addressed cross-project deletion. Fix `654d2c704` constrained deletion by `project_id` but did not change the permission-tier check. - [GHSA-qfwc-vx6f-3g6g](https://github.com/go-vikunja/vikunja/security/advisories/GHSA-qfwc-vx6f-3g6g) addressed share-hash disclosure through by-ID reads. - [GHSA-8hp8-9fhr-pfm9](https://github.com/go-vikunja/vikunja/security/advisories/GHSA-8hp8-9fhr-pfm9) addressed share-hash disclosure through listing. - [GHSA-96q5-xm3p-7m84 / CVE-2026-35594](https://github.com/go-vikunja/vikunja/security/advisories/GHSA-96q5-xm3p-7m84) addressed tokens remaining valid after deletion. That fix does not prevent unauthorized deletion. ## Credit Reported via mail.

Source published

9 Oct 2026 20:57:47 UTC

Source modified

27 Oct 2026 15:30:05 UTC

Observed here

27 Oct 2026 15:46:08 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

Publisher rating · MODERATE

Vikunja: Write-level project members can delete admin-tier link shares through an unloaded permission check in code.vikunja.io/api. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: .

Source published

19 Oct 2026 21:08:26 UTC

Source modified

19 Oct 2026 21:41:16 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.