CVE-2026-91973

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-15. a secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this weekElevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: Elevated riskExposed: 0

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

Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV BasicAuth endpoints that lack rate limiting protection. Remote unauthenticated attackers can issue unbounded credential-guessing requests against /dav, /.well-known, and /feeds routes to bypass the instance's anti-brute-force controls and compromise password-only accounts.

CVSS v3
7.5
EG Score
7.5(high)
EG Risk
65(Attend)
EG Risk 65/100SSVC: Attend

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
Severity75% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
48%
KEV
Not listed

Published

September 15, 2026

Last Modified

September 16, 2026

Advisory Details (2)

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

Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth | Advisories | VulnCheck

https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth
github Patch Available🟡 PoC Available

CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords · Advisory · go-vikunja/vikunja · GitHub

https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2

Vendor Advisories for CVE-2026-91973(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 21× in last 7d / 21× 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. 2026-09-19 17:49 UTCEG score recompute
  2. 2026-09-19 17:49 UTCGHSA enrichment
  3. 2026-09-19 06:22 UTCEG score recompute
  4. 2026-09-19 06:22 UTCGHSA enrichment
  5. 2026-09-18 19:28 UTCEPSS rescore
  6. 2026-09-18 18:56 UTCGHSA enrichment
  7. 2026-09-18 07:29 UTCGHSA enrichment
  8. 2026-09-17 20:02 UTCEG score recompute
  9. 2026-09-17 20:02 UTCGHSA enrichment
  10. 2026-09-17 19:32 UTCEPSS rescore
  11. 2026-09-17 08:33 UTCGHSA enrichment
  12. 2026-09-16 21:07 UTCGHSA enrichment
  13. 2026-09-16 15:34 UTCEG score recompute
  14. 2026-09-16 15:34 UTCGHSA enrichment
  15. 2026-09-16 14:09 UTCEPSS rescore
  16. 2026-09-16 04:01 UTCEG score recompute
  17. 2026-09-16 04:01 UTCGHSA enrichment
  18. 2026-09-15 16:32 UTCEG score recompute
  19. 2026-09-15 16:03 UTCEG score recompute
  20. 2026-09-15 15:23 UTCEG score recompute
  21. 2026-09-15 15:22 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-91973?
CVE-2026-91973 is a high vulnerability published on September 15, 2026. Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV BasicAuth endpoints that lack rate limiting protection. Remote unauthenticated attackers can issue unbounded credential-guessing requests against /dav, /.well-known, and /feeds routes to bypass the instance's…
When was CVE-2026-91973 disclosed?
CVE-2026-91973 was first published in the National Vulnerability Database on September 15, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-91973 actively exploited?
CVE-2026-91973 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 52.2% of all scored CVEs.
What is the CVSS score of CVE-2026-91973?
CVE-2026-91973 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-91973?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-91973, 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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