dbcve.org
Cal.comApplication · Cal

CVE-2026-23478

CRITICAL · 9.8 CVSS v3.1 Published 2026-01-13
Fix available
A fix is available. Upgrade to 6.0.7 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Authentication bypass in Cal.com's custom NextAuth JWT callback allows attackers to supply a target email via session.update() to gain full authenticated access to any user account. This affects versions 3.1.6 through 6.0.6.

MitigationUpgrade to Cal.com version 6.0.7 or later to patch the vulnerable JWT callback logic.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Cal.comApplication
Affected:>= 3.1.6, < 6.0.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Cal.com installation version
    Check package.json in the Cal.com root directory for the 'version' field, or run 'npm list @calcom/lib' or check the admin settings page for version info
    Affected if Installed version is >= 3.1.6 and < 6.0.7
  2. Locate NextAuth configuration
    Search for the NextAuth API route file - typically at pages/api/auth/[...nextauth].ts, pages/api/auth/[...nextauth].js, or app/api/auth/[...nextauth]/route.ts in the Cal.com installation
    Affected if A custom NextAuth configuration file exists with a JWT callback defined
  3. Inspect JWT callback implementation
    Open the NextAuth configuration file and locate the 'callbacks' section with 'jwt' function. Examine the code inside for any logic that processes or passes the email from the session or token to the JWT payload
    Affected if A custom JWT callback exists that processes email from session data
  4. Check for vulnerable session.update() usage
    Search the codebase for files containing 'session.update(' or 'await session.update(' to identify where session updates are being performed, particularly where user-supplied data might be passed
    Affected if session.update() is called with user-controlled or external email parameter without proper server-side validation

Your environment is affected if Cal.com version is between 3.1.6 and 6.0.6 inclusive AND custom NextAuth JWT callback with session.update() usage exists in the codebase.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.0.7 or later
Fixed in 6.0.7
Interim mitigation

Upgrade to Cal.com version 6.0.7 or later to patch the vulnerable JWT callback logic.

Recommended fix High confidence

6.0.7

  1. Backup your Cal.com database and configuration files before proceeding with the upgrade
  2. Check your current Cal.com version to confirm it is vulnerable (between 3.1.6 and 6.0.6 inclusive)
  3. Upgrade Cal.com to version 6.0.7 or later using your package manager (e.g., npm install @calcom/[email protected] or docker pull calcom/docker:6.0.7)
  4. After upgrading, restart all Cal.com services
  5. Verify the upgrade was successful by checking the version and testing authentication functionality

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Cal.com Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-23478 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data