Security readout for executives and security teams
Plain-English summary
Cal.com versions 3.1.6 through before 6.0.7 allow an unauthenticated attacker to impersonate any user by abusing email handling in authentication. This can give full account access. For organizations running affected self-hosted Cal.com, urgency is critical because compromise does not require user interaction or prior access.
Executive priority
Treat as an emergency for affected deployments. The flaw enables account takeover without credentials, creating risk to scheduling data, integrations, and privileged Cal.com administration. Patch validation should be tracked to completion.
Technical view
The issue is an authentication bypass in Cal.com’s custom NextAuth JWT callback. The advisory says a supplied target email via session.update() was not validated, allowing full authenticated access to any user account. Affected versions are >=3.1.6 and <6.0.7. Fixed version is 6.0.7. CVSS v4.0 score is 10.0.
Likely exposure
Exposure is likely limited to organizations running self-hosted Cal.com versions 3.1.6 through 6.0.6. The sources do not state whether Cal.com hosted cloud instances were affected or remediated.
Exploitation context
The CVSS vector indicates network exploitation, low complexity, no privileges, and no user interaction. The provided sources do not report active exploitation, and the CVE is not listed as KEV in the bundle.
Researcher notes
Mapped weaknesses are CWE-602 and CWE-639. Focus review on trust boundaries in session update handling, JWT callback logic, and whether email identity is derived from trusted server-side state. Avoid assuming exploit activity without additional telemetry.
Mitigation direction
- Upgrade Cal.com to version 6.0.7 or later.
- Prioritize internet-facing Cal.com deployments first.
- If immediate upgrade is impossible, check Cal.com vendor guidance for temporary controls.
- Review authentication and session-related logs for suspicious account switching indicators.
Validation and detection
- Inventory all Cal.com deployments and record running versions.
- Confirm affected instances are not between 3.1.6 and 6.0.6.
- Verify the upgrade to 6.0.7 or later completed successfully.
- Review user sessions and administrative activity during the exposure window.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-602: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-639: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-23478 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 10 (4.0)
- Known Exploited
- No
- Published
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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
10CriticalVector: 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
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/calcom/cal.com/security/advisories/GHSA-7hg4-x4pr-3hrgCVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Client-Side Enforcement of Server-Side Security
Client-Side Enforcement of Server-Side Security represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Authorization Bypass Through User-Controlled Key
Authorization Bypass Through User-Controlled Key represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.