# CVE-2026-123526: Vikunja before 2.7.1 Mass Assignment via Team external_id Field

Status: published. Published: 2026-11-08. Updated: 2026-11-09.

Vikunja before 2.7.1 contains a mass assignment vulnerability that allows any authenticated user to set the read-only external_id field through the team create and update endpoints. Attackers can tag a team they create or administer as externally managed, permanently blocking removal of every member and causing SSO members to be dropped from the team at their next login.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- go-vikunja / vikunja (code.vikunja.io/api): ≥ 0; < 2.7.1 (affected, semver); 2.7.1 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 5.3 (medium); 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; source: CNA: VulnCheck

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L; source: CNA: VulnCheck

- CVSS 4.0: 5.3 (medium); 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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.26% as of 2026-11-09; percentile 17.32%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-915

## Exploit evidence

- exploit: https://github.com/go-vikunja/vikunja/security/advisories/GHSA-fjrf-gjmg-9v6g (ADP: CISA-ADP)

## References

- https://github.com/go-vikunja/vikunja/security/advisories/GHSA-fjrf-gjmg-9v6g (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/vikunja-before-2.7.1-mass-assignment-via-team-external-id-field (CNA: VulnCheck; third-party-advisory)

- https://github.com/go-vikunja/vikunja/security/advisories/GHSA-fjrf-gjmg-9v6g (ADP: CISA-ADP; exploit)

- https://github.com/go-vikunja/vikunja/security/advisories/GHSA-fjrf-gjmg-9v6g (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/vikunja-before-2.7.1-mass-assignment-via-team-external-id-field (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-123526; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123526; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-123526; retrieved 2026-11-09; source updated Not reported

Revision: e8d5f36bf0960aa86de47c310ce68ee2233fb9fb2bd62f16978462a2f3561ca5

Canonical: https://y2.dev/cve/CVE-2026-123526

## Agent and API access

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- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.