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

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

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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(). …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

Send crafted session.update() request with target email

Exploit

Bypass JWT callback validation

Execution

Hijack authenticated session

Impact

Access victim's account

Access

Send crafted session.update() request with target email

Exploit

Bypass JWT callback validation

Execution

Hijack authenticated session

Impact

Access victim's account

Vulnerability AssessmentAI

Exploitation	Cal.com versions 3.1.6 through 6.0.6 with custom NextAuth JWT callback enabled. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	CVSS 9.8 (Critical). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	An attacker creates an account on Cal.com, then calls session.update() with the target user's email. Their session is updated to the target's account, granting full access to their calendar, bookings, and connected integrations.
Remediation	Update to Cal.com 6.0.7. Detailed patch versions, workarounds, and compensating controls in full report.