What is CVE-2025-66489?

CVE-2025-66489 is a critical-severity vulnerability in Cal Cal.com, classified under Incorrect Implementation of Authentication Algorithm. CVSS score: 9.8/10. Published 2025-12-03.

How severe is CVE-2025-66489?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Cal Cal.com

CVE-2025-66489

Cal.com is open-source scheduling software. Prior to 5.9.8, A flaw in the login credentials provider allows an attacker to bypass password verification when a TOTP code is provided, potentially gaining unauthorized access to user accounts. This issue exists due to problematic conditional logic in the authentication flow. This vulnerability is fixed in 5.9.8.

Published 2025-12-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.008 (56.2th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Cal Cal.com
Calcom Cal.com — versions < 5.9.8

Weakness classification (CWE)

CWE-303 — Incorrect Implementation of Authentication Algorithm

References

github.com/calcom/cal.com/security/advisories/GHSA-9r3w-4j8q-pw98 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2025-66489?: CVE-2025-66489 is a critical-severity vulnerability in Cal Cal.com, classified under Incorrect Implementation of Authentication Algorithm. CVSS score: 9.8/10. Published 2025-12-03.
How severe is CVE-2025-66489?: Critical severity. CVSS v3 base score is 9.8 out of 10.