Vulnerability · Published Jan 13, 2026 · Assigned by GitHub_M

CVE-2026-23478Cal.com has an Authentication Bypass via Unvalidated Email in Custom JWT Callback

Critical 10.0

In plain English

A critical-severity authorization bypass via user-controlled key in cal.com from calcom. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).

Severity (CVSS 4.0)10.0Critical

Exploit odds (30 days)0.5%top 59.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

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

Weakness: CWE-602, CWE-639 · 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

References

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