In some mod_ssl configurations on Apache HTTP Server versions 2.4.35 through 2.4.63, an access control bypass by trusted clients is possible using TLS 1.3 session resumption. Configurations are affected when mod_ssl is configured for multiple virtual hosts, with each restricted to a different set of trusted client certificates. In such cases, a client trusted to access one virtual host may be able to access another virtual host if SSLStrictSNIVHostCheck is not enabled in either virtual host.
The severity level of this vulnerability is classified as critical with a CVSS score of 9.1. This high score indicates significant risk to organizations, particularly in environments where different virtual hosts are employed with varying access controls.
Risk to organizations includes unauthorized access to sensitive data or resources, which can have serious implications for data integrity and confidentiality. As a result, organizations should prioritize patching immediately to mitigate potential risks.
The exploitation status of this vulnerability is confirmed, with known exploit techniques available. Organizations should be particularly vigilant and address this vulnerability as part of their immediate security priorities.
Given the potential for significant impact, organizations must act promptly to secure their Apache HTTP Server configurations.
Vulnerability Details
The vulnerability allows trusted clients to bypass access controls in Apache HTTP Server versions 2.4.35 through 2.4.63 when mod_ssl is configured for multiple virtual hosts.
The CVSS score for this vulnerability is 9.1, indicating a critical severity level. This score reflects the potential for significant impact on confidentiality and integrity, making it imperative for organizations to act swiftly.
The affected component is the Apache HTTP Server, specifically the mod_ssl module. The vulnerability was published on July 10, 2025, and the CWE classification is CWE-284.
Technical Analysis
The root cause of this vulnerability lies in the misconfiguration of mod_ssl settings across multiple virtual hosts. When different virtual hosts are configured with different trusted client certificates, the absence of SSLStrictSNIVHostCheck allows a client trusted for one virtual host to access another virtual host.
The attack vector for this vulnerability is network-based, where attackers can exploit the access control bypass through existing trusted client certificates. The attack complexity is low, requiring no special privileges or user interaction.
The confidentiality impact is high as sensitive information may be accessed without authorization. Integrity is also at risk, but availability remains unaffected.
Risk & Impact Analysis
The real-world deployment risk associated with this vulnerability is significant, particularly for organizations using Apache HTTP Server with multiple virtual hosts. The potential for unauthorized access to sensitive data can lead to severe data breaches and compliance violations.
Organizations must understand the implications of this vulnerability as it can affect not only their data integrity but also their reputation and trust with customers. The urgency for addressing this vulnerability is high given the CVSS score and the availability of known exploits.
The potential blast radius includes any resources exposed by the affected virtual hosts, which could lead to widespread consequences across organizational operations.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Affected versions include Apache HTTP Server from 2.4.35 to 2.4.63. Organizations running these versions should apply patches or updates provided by Apache.
Mitigation & Remediation
Organizations should update to Apache HTTP Server version 2.4.64 or later to mitigate this vulnerability. If an immediate upgrade is not possible, consider implementing configuration hardening practices. This includes enabling the SSLStrictSNIVHostCheck directive for virtual hosts.
For additional security, organizations may also want to consider conducting a comprehensive security assessment through application security assessment and continuous penetration testing.
Monitoring access logs for unusual patterns and conducting regular security audits will also help in identifying potential exploitation attempts.
Detection Guidance
Organizations should monitor their Apache HTTP Server logs for indicators of unauthorized access, specifically looking for anomalies in client certificate authentication. Behavioral anomalies, such as repeated access from unexpected client certificates, should be flagged for further investigation.
Additionally, network signatures that identify unusual access patterns across virtual hosts can provide an early warning of potential exploitation.
AppSecure Threat Intelligence Insight
This vulnerability underscores the importance of proper configuration management in web server environments. Security teams should take this incident as a learning opportunity to review their access control policies and ensure that all configurations adhere to best practices.
The trend of access control vulnerabilities highlights the need for ongoing security awareness training and robust security validation processes. As organizations increasingly rely on complex configurations, the potential for oversights grows.
For further insights into securing web applications, organizations can explore our guidelines on web application penetration testing and the importance of continuous security testing.
Security teams should also consider the implications of such vulnerabilities on their incident response plans, ensuring they are prepared for potential exploitation scenarios.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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