CVE-2026-23478

Unknown Unknown - Not Provided

Authentication Bypass in Cal.com NextAuth JWT Callback

Publication date: 2026-01-13

Last updated on: 2026-02-03

Assigner: GitHub, Inc.

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-01-13

Last Modified

2026-02-03

Generated

2026-07-06

AI Q&A

2026-01-14

EPSS Evaluated

2026-07-05

NVD

CVE-2026-23478

EUVD

EUVD-2026-2413

Affected Vendors & Products

Vendor	Product	Version / Range
calcom	cal.com	From 3.1.6 (inc) to 6.0.7 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-602	The product is composed of a server that relies on the client to implement a mechanism that is intended to protect the server.
CWE-639	The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.

Attack-Flow Graph

Executive Summary

This vulnerability exists in Cal.com scheduling software versions from 3.1.6 to before 6.0.7. It is due to a flaw 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 the session.update() function. This means an attacker can impersonate any user without proper authorization.

Impact Analysis

The vulnerability allows attackers to gain full authenticated access to any user's account, which can lead to unauthorized access to sensitive scheduling information, potential data theft, manipulation of user data, and loss of trust in the system's security.

Mitigation Strategies

Upgrade Cal.com scheduling software to version 6.0.7 or later, as this version contains the fix for the vulnerability in the custom NextAuth JWT callback that allows attackers to gain full authenticated access by supplying a target email address via session.update().

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