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CVE-2026-35594

Vikunja Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade

6.5 MediumFix available

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's link share authentication (GetLinkShareFromClaims in pkg/models/link_sharing.go) constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl). This vulnerability is fixed in 2.3.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
None

Exploit likelihood

0.32%Up 0.3 points since Apr 11, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.5

Vikunja Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's link share authentication (GetLinkShareFromClaims in pkg/models/link_sharing.go) constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl). This vulnerability is fixed in 2.3.0.

Record
CVE-2026-35594
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness
CWE-613
Updated
2026-11-02
EUVDEUVD-2026-21417 6.5

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's link share authentication (GetLinkShareFromClaims in pkg/models/link_sharing.go) constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl). This vulnerability is fixed in 2.3.0.

Record
EUVD-2026-21417
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-96q5-xm3p-7m84 6.5

Vikunja: Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade

Title

Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade

Description

Vikunja's link share authentication constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl).

GetLinkShareFromClaims at pkg/models/link_sharing.go lines 88-119 performs zero database queries — it builds the LinkSharing struct purely from JWT claim values (id, hash, project_id, permission, sharedByID). This struct is passed directly to permission checks:

| Function | File | Lines | DB queries | |----------|------|-------|------------| | GetLinkShareFromClaims | link_sharing.go | 88-119 | 0 | | Project.CanRead (link share) | project_permissions.go | 105-108 | 0 | | Project.CanWrite (link share) | project_permissions.go | 50-53 | 0 | | Project.IsAdmin (link share) | project_permissions.go | 192-194 | 0 |

Contrast with user tokens: User JWTs use a 10-minute TTL (ServiceJWTTTLShort) with sid claim and server-side sessions enabling revocation. Link share JWTs use a 72-hour TTL (ServiceJWTTTL) with no sid, no server-side session, and no refresh mechanism.

Permalink:

  • GetLinkShareFromClaims: pkg/models/link_sharing.go:88-119
  • NewLinkShareJWTAuthtoken: pkg/modules/auth/auth.go:141-160
  • Permission checks: pkg/models/project_permissions.go:50-53, 105-108, 192-194
  • TTL defaults: pkg/config/config.go:337-339

PoC

# 1. Create an Admin-level link share on project 42
curl -X PUT "https://vikunja.example.com/api/v1/projects/42/shares" \
  -H "Authorization: Bearer <owner-jwt>" \
  -H "Content-Type: application/json" \
  -d '{"permission": 2}'
# Response: {"id": 5, "hash": "abc123", ...}

# 2. Obtain link share JWT (72h TTL, no sid claim)
curl -X POST "https://vikunja.example.com/api/v1/shares/abc123/auth"
# Response: {"token": "<link-share-jwt>"}

# 3. Delete the link share
curl -X DELETE "https://vikunja.example.com/api/v1/projects/42/shares/5" \
  -H "Authorization: Bearer <owner-jwt>"
# 200 OK — share row removed from database

# 4. Use the deleted share's JWT — STILL WORKS for up to 72 hours
curl -X GET "https://vikunja.example.com/api/v1/projects/42/tasks" \
  -H "Authorization: Bearer <link-share-jwt>"
# 200 OK — full task list returned with Admin permissions

# 5. Permission downgrade variant:
# Delete Admin share → create Read-only share → old JWT still has Admin access

Impact

  • Revoked link shares remain functional for up to 72 hours (default TTL)
  • Project owners cannot respond to security events (leaked URLs, access revocation) in real time
  • Permission downgrades have no effect on outstanding tokens
  • Scope: single project per token, severity scales with permission level (Admin > Write > Read)

Fix

Add database validation in GetLinkShareFromClaims:

func GetLinkShareFromClaims(claims jwt.MapClaims) (share *LinkSharing, err error) {
    id, is := claims["id"].(float64)
    if !is {
        return nil, &ErrLinkShareTokenInvalid{}
    }
    // Validate against database
    s := db.NewSession()
    defer s.Close()
    share, err = GetLinkShareByID(s, int64(id))
    if err != nil {
        return nil, err  // Share was deleted
    }
    // Verify permission not downgraded
    claimedPermission := Permission(claims["permission"].(float64))
    if share.Permission < claimedPermission {
        return nil, &ErrLinkShareTokenInvalid{}
    }
    return share, nil
}

Alternatives: shorter TTL with refresh mechanism, token blocklist, or session tracking matching user token pattern.

Record
GHSA-96q5-xm3p-7m84
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness
CWE-613
Updated
2026-11-02
NVD 6.5

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's link share authentication (GetLinkShareFromClaims in pkg/models/link_sharing.go) constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl). This vulnerability is fixed in 2.3.0.

Record
CVE-2026-35594
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness
CWE-613
Updated
2026-11-02
OSV 6.5

Vikunja Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's link share authentication (GetLinkShareFromClaims in pkg/models/link_sharing.go) constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl). This vulnerability is fixed in 2.3.0.

Record
CVE-2026-35594
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness
CWE-613
Updated
2026-11-02
OSVGHSA-96q5-xm3p-7m84 6.5

Vikunja: Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade

Title

Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade

Description

Vikunja's link share authentication constructs authorization objects entirely from JWT claims without any server-side database validation. When a project owner deletes a link share or downgrades its permissions, all previously issued JWTs continue to grant the original permission level for up to 72 hours (the default service.jwtttl).

GetLinkShareFromClaims at pkg/models/link_sharing.go lines 88-119 performs zero database queries — it builds the LinkSharing struct purely from JWT claim values (id, hash, project_id, permission, sharedByID). This struct is passed directly to permission checks:

| Function | File | Lines | DB queries | |----------|------|-------|------------| | GetLinkShareFromClaims | link_sharing.go | 88-119 | 0 | | Project.CanRead (link share) | project_permissions.go | 105-108 | 0 | | Project.CanWrite (link share) | project_permissions.go | 50-53 | 0 | | Project.IsAdmin (link share) | project_permissions.go | 192-194 | 0 |

Contrast with user tokens: User JWTs use a 10-minute TTL (ServiceJWTTTLShort) with sid claim and server-side sessions enabling revocation. Link share JWTs use a 72-hour TTL (ServiceJWTTTL) with no sid, no server-side session, and no refresh mechanism.

Permalink:

  • GetLinkShareFromClaims: pkg/models/link_sharing.go:88-119
  • NewLinkShareJWTAuthtoken: pkg/modules/auth/auth.go:141-160
  • Permission checks: pkg/models/project_permissions.go:50-53, 105-108, 192-194
  • TTL defaults: pkg/config/config.go:337-339

PoC

# 1. Create an Admin-level link share on project 42
curl -X PUT "https://vikunja.example.com/api/v1/projects/42/shares" \
  -H "Authorization: Bearer <owner-jwt>" \
  -H "Content-Type: application/json" \
  -d '{"permission": 2}'
# Response: {"id": 5, "hash": "abc123", ...}

# 2. Obtain link share JWT (72h TTL, no sid claim)
curl -X POST "https://vikunja.example.com/api/v1/shares/abc123/auth"
# Response: {"token": "<link-share-jwt>"}

# 3. Delete the link share
curl -X DELETE "https://vikunja.example.com/api/v1/projects/42/shares/5" \
  -H "Authorization: Bearer <owner-jwt>"
# 200 OK — share row removed from database

# 4. Use the deleted share's JWT — STILL WORKS for up to 72 hours
curl -X GET "https://vikunja.example.com/api/v1/projects/42/tasks" \
  -H "Authorization: Bearer <link-share-jwt>"
# 200 OK — full task list returned with Admin permissions

# 5. Permission downgrade variant:
# Delete Admin share → create Read-only share → old JWT still has Admin access

Impact

  • Revoked link shares remain functional for up to 72 hours (default TTL)
  • Project owners cannot respond to security events (leaked URLs, access revocation) in real time
  • Permission downgrades have no effect on outstanding tokens
  • Scope: single project per token, severity scales with permission level (Admin > Write > Read)

Fix

Add database validation in GetLinkShareFromClaims:

func GetLinkShareFromClaims(claims jwt.MapClaims) (share *LinkSharing, err error) {
    id, is := claims["id"].(float64)
    if !is {
        return nil, &ErrLinkShareTokenInvalid{}
    }
    // Validate against database
    s := db.NewSession()
    defer s.Close()
    share, err = GetLinkShareByID(s, int64(id))
    if err != nil {
        return nil, err  // Share was deleted
    }
    // Verify permission not downgraded
    claimedPermission := Permission(claims["permission"].(float64))
    if share.Permission < claimedPermission {
        return nil, &ErrLinkShareTokenInvalid{}
    }
    return share, nil
}

Alternatives: shorter TTL with refresh mechanism, token blocklist, or session tracking matching user token pattern.

Record
GHSA-96q5-xm3p-7m84
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness
CWE-613
Updated
2026-11-02
OSVGO-2026-5276 No score

Vikunja: Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade in code.vikunja.io/api

Vikunja: Link Share JWT tokens remain valid for 72 hours after share deletion or permission downgrade 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: code.vikunja.io/api before v2.3.0.

Record
GO-2026-5276
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
code.vikunja.io/api
Go
 through 2.2.2
2.3.0
code.vikunja.io/api
Go
 before 2.3.0
2.3.0
code.vikunja.io/api
Go
 All versions None known
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-35594 is a medium vulnerability (CVSS 6.5) in Go-vikunja Vikunja, published April 10, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.32%, the 24th percentile. Fixed in code.vikunja.io/api 2.3.0.

References

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