CVE-2026-23478 identifies a critical vulnerability in Cal.com, an open-source scheduling software. This vulnerability, present in versions 3.1.6 to before 6.0.7, allows attackers to gain full authenticated access to any user's account by supplying a target email address via session.update(). With a CVSS score of 10, this vulnerability poses a significant risk to organizations utilizing Cal.com.
The vulnerability is due to improper handling of JWT callbacks, which can lead to unauthorized access. As a result, attackers can manipulate user sessions, leading to potential data breaches and unauthorized actions within user accounts. Organizations should prioritize patching to the fixed version, 6.0.7, to mitigate this risk.
Risk to organizations includes unauthorized account access, data exposure, and potential integrity violations. The urgency for defenders is critical due to the high CVSS score and the potential impact on user trust and data confidentiality.
Currently, there are no known public exploits or proof of concepts, and the vulnerability has not been added to the KEV catalog. However, organizations should remain vigilant and monitor for any updates regarding exploitation.
Organizations should prioritize patching immediately.
Vulnerability Details
The official CVE description indicates that the vulnerability in Cal.com is associated with a custom NextAuth JWT callback. The affected versions, ranging from 3.1.6 to before 6.0.7, are susceptible to unauthorized access through session updates. The vulnerability is classified under CWE-602 and CWE-639.
The CVSS score of 10 denotes a critical severity level, indicating a high level of concern for potential impacts on confidentiality, integrity, and availability. Organizations using the affected versions must upgrade to 6.0.7 to remediate this vulnerability.
Technical Analysis
The root cause of this vulnerability is the insecure implementation of the JWT callback within the Cal.com application. The attack vector is network-based, allowing remote attackers to exploit this vulnerability without any required privileges or user interaction.
The attack complexity is low, as attackers can easily provide a target email address to gain unauthorized access. This exploitation can lead to a high impact on confidentiality, integrity, and availability, given the nature of the access gained.
Risk & Impact Analysis
Real-world deployment of this vulnerability poses severe risks, including unauthorized access to user data, which can compromise sensitive information. Organizations using Cal.com should be concerned about the potential for widespread account takeovers, leading to data breaches and reputational damage.
With a CVSS score of 10, the urgency for organizations is critical. Immediate action is required to mitigate the risk associated with this vulnerability, as the potential blast radius is extensive, impacting all users of affected versions.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions of Cal.com prior to 6.0.7 are affected by this vulnerability. Organizations using versions 3.1.6 to 6.0.6 should upgrade to the latest version to mitigate the risk.
Mitigation & Remediation
Organizations should upgrade to Cal.com version 6.0.7 or later to remediate this vulnerability. If immediate patching is not possible, organizations should consider implementing network controls to restrict access to the application.
In addition to upgrading, organizations should conduct a thorough review of their authentication mechanisms and implement configuration hardening to minimize the risk of similar vulnerabilities in the future.
For ongoing security assurance, organizations can engage in penetration testing to identify potential weaknesses.
Detection Guidance
Organizations should monitor logs for any unusual authentication attempts or session updates that do not align with user activity. Additionally, behavioral anomalies should be investigated to identify any potential exploitation of this vulnerability.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2026-23478 highlights the importance of secure coding practices, particularly in authentication systems. Organizations should learn from this incident to bolster their security postures and avoid similar vulnerabilities.
This vulnerability serves as a reminder to regularly review and test authentication mechanisms. Security teams should engage in proactive measures to ensure that their systems are resilient against potential attacks.
For further insights into securing applications, organizations can refer to our application security assessment resources and consider adopting a comprehensive approach to security.
Organizations should remain vigilant and prepared to respond to emerging vulnerabilities in the software they utilize.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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