What is the CVSS score of CVE-2026-23478?

CVE-2026-23478 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.1%.

Which versions of Cal.Com are affected by CVE-2026-23478?

Organizations using Cal.com face critical risk from CVE-2026-23478 rated CVSS 9.8.

How to fix or mitigate CVE-2026-23478?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. Monitor vendor channels for patch availability.

Cal.Com CVE-2026-23478

CRITICAL

Client-Side Enforcement of Server-Side Security (CWE-602)

2026-01-13 security-advisories@github.com

Information Disclosure Cal.Com Cal Cal Com

9.8

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

CVE Published

Jan 13, 2026 - 22:16 nvd

CRITICAL 9.8

DescriptionGitHub Advisory

Cal.com is open-source scheduling software. From 3.1.6 to before 6.0.7, there is a vulnerability in a custom NextAuth JWT callback that allows attackers to gain full authenticated access to any user's account by supplying a target email address via session.update(). This vulnerability is fixed in 6.0.7.

AnalysisAI

Cal.com scheduling software (3.1.6 to 6.0.7) has a critical authentication bypass in the NextAuth JWT callback. Attackers can gain full access to any user account by supplying a target email via session.update(). Fixed in 6.0.7.

Technical ContextAI

A custom NextAuth JWT callback allows the session.update() function to change the authenticated user by accepting a target email address (CWE-602). An attacker can update their session to point to any user account.