CVE-2026-91981

MEDIUMPre-NVD 4.34.3—
EchelonGraph scoreHIGH confidence

Score 4.3 from GitHub Security Advisory published 2026-09-15. a secondary CVSS source baseline 4.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this weekElevated
4.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 4.3Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Vikunja versions before 2.6.0 fail to properly validate link-share tokens in the v2 API user search endpoints. Attackers with a read-only share link can enumerate project users via the projects endpoint and confirm arbitrary usernames exist via the global search endpoint.

CVSS v3
4.3
EG Score
4.3(high)
EG Risk
35(Track)
EG Risk 35/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity43% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
21%
KEV
Not listed

Published

September 15, 2026

Last Modified

September 21, 2026

Advisory Details (2)

Auto-updated Sep 15, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

Vikunja before 2.6.0 User Enumeration via v2 API | Advisories | VulnCheck

https://www.vulncheck.com/advisories/vikunja-before-2.6.0-user-enumeration-via-v2-api
github Patch Available🟡 PoC Available

Link-share token can enumerate users through the v2 API · Advisory · go-vikunja/vikunja · GitHub

https://github.com/go-vikunja/vikunja/security/advisories/GHSA-vfxw-3x8p-2vjr

Vendor Advisories for CVE-2026-91981(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 23× in last 7d / 33× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-24 17:09 UTCEG score recompute
  2. 2026-09-24 17:09 UTCGHSA enrichment
  3. 2026-09-24 14:04 UTCEPSS rescore
  4. 2026-09-23 17:56 UTCEG score recompute
  5. 2026-09-23 17:56 UTCGHSA enrichment
  6. 2026-09-23 17:54 UTCEPSS rescore
  7. 2026-09-22 18:43 UTCEG score recompute
  8. 2026-09-22 18:43 UTCGHSA enrichment
  9. 2026-09-22 16:01 UTCEPSS rescore
  10. 2026-09-21 21:09 UTCEPSS rescore
  11. 2026-09-21 19:31 UTCEG score recompute
  12. 2026-09-21 19:31 UTCGHSA enrichment
  13. 2026-09-21 18:55 UTCEG score recompute
  14. 2026-09-21 18:55 UTCGHSA enrichment
  15. 2026-09-21 17:10 UTCEG score recompute
  16. 2026-09-21 17:10 UTCGHSA enrichment
  17. 2026-09-20 20:16 UTCEPSS rescore
  18. 2026-09-20 17:57 UTCGHSA enrichment
  19. 2026-09-19 18:43 UTCEG score recompute
  20. 2026-09-19 18:43 UTCGHSA enrichment
  21. 2026-09-18 19:31 UTCEG score recompute
  22. 2026-09-18 19:31 UTCGHSA enrichment
  23. 2026-09-18 19:28 UTCEPSS rescore
  24. 2026-09-17 20:19 UTCEG score recompute
  25. 2026-09-17 20:19 UTCGHSA enrichment
Show 8 more
  1. 2026-09-17 19:32 UTCEPSS rescore
  2. 2026-09-16 21:07 UTCGHSA enrichment
  3. 2026-09-16 15:45 UTCEG score recompute
  4. 2026-09-16 15:45 UTCGHSA enrichment
  5. 2026-09-16 14:09 UTCEPSS rescore
  6. 2026-09-15 16:32 UTCEG score recompute
  7. 2026-09-15 15:23 UTCEG score recompute
  8. 2026-09-15 15:22 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-91981?
CVE-2026-91981 is a medium vulnerability published on September 15, 2026. Vikunja versions before 2.6.0 fail to properly validate link-share tokens in the v2 API user search endpoints. Attackers with a read-only share link can enumerate project users via the projects endpoint and confirm arbitrary usernames exist via the global search endpoint.
When was CVE-2026-91981 disclosed?
CVE-2026-91981 was first published in the National Vulnerability Database on September 15, 2026, with the most recent update on September 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-91981 actively exploited?
CVE-2026-91981 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 79.2% of all scored CVEs.
What is the CVSS score of CVE-2026-91981?
CVE-2026-91981 has a CVSS v3 base score of 4.3 (NVD).
How do I remediate CVE-2026-91981?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-91981, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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