CVE-2026-23478 PUBLISHED

Cal.com has an Authentication Bypass via Unvalidated Email in Custom JWT Callback

Assigner: GitHub_M
Reserved: 13.01.2026 Published: 13.01.2026 Updated: 14.01.2026

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.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:L
CVSS Score: 10

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	High
Attack Complexity	Low	Integrity	High	Integrity	High
Attack Requirements	None	Availability	High	Availability	Low
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	calcom
Product	cal.com
Versions	Version >= 3.1.6, < 6.0.7 is affected

References

https://github.com/calcom/cal.com/security/advisories/GHSA-7hg4-x4pr-3hrg

Problem Types

CWE-602: Client-Side Enforcement of Server-Side Security CWE
CWE-639: Authorization Bypass Through User-Controlled Key CWE