CVE-2025-66489: Cal.com is open-source scheduling software

Q: How do I fix CVE-2025-66489?

cal.com: upgrade to 5.9.8. Exact commands for each OS are on this page.

Q: Is CVE-2025-66489 being exploited?

CVE-2025-66489 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2025-66489 affect?

CVE-2025-66489 affects cal.com. Severity is critical (CVSS 9.8). 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.

Q: How urgent is CVE-2025-66489?

Priority 60/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2025-66489 is a critical-severity flaw (CVSS 9.8) affecting cal.com. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 38%)
CISA exploited list	No
Weakness	CWE-303
Published	2025-12-03
Last modified	2026-10-18

Publisher (CNA): GitHub, Inc. · Vendor: cal

Last updated 2026-10-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-12-03 20:16 UTCPublished CVE record published
2026-10-18 18:10 UTCUpdated Record last modified

cal cal.com UPGRADE

Affected: < 5.9.8

Fixed in: 5.9.8

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cal.com || rpm -q cal.com || cal.com --version

2. UPGRADE to 5.9.8 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cal.com

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cal.com

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

Fedora 46 · legofy · FIXED · 1.0.0-43.20261028git6913585.fc46 · FEDORA-2026-e1e60e1e32 · source

sudo dnf upgrade --advisory=FEDORA-2026-e1e60e1e32

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-66489?

cal.com: upgrade to 5.9.8. Exact commands for each OS are on this page.

Is CVE-2025-66489 being exploited?

CVE-2025-66489 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-66489 affect?

CVE-2025-66489 affects cal.com. Severity is critical (CVSS 9.8). 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.

How urgent is CVE-2025-66489?

Priority 60/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-23478 CRITICAL 9.8 UPGRADE Cal.com is open-source scheduling software

References

← Back to latest CVEs