CVE-2026-73581 in Tomcat
Summary
by MITRE • 09/23/2026
Improper Check for Certificate Revocation vulnerability in Apache Tomcat. Both the OpenSSL and OpenSSL-FFM TLS implementations ignore CRLs when certificate uses a keystore.
This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.58, from 9.0.0-M1 through 9.0.121.
The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.0 through 8.5.100. Other unsupported versions may also be affected.
Users are recommended to upgrade to version 11.0.26, 10.1.59, 9.0.122, which fixes the issue.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability identified as Improper Check for Certificate Revocation in Apache Tomcat represents a critical failure in the transport layer security validation process when utilizing specific keystore configurations. This flaw affects multiple major branches of the software, including versions 11.0 through 11.0.25, 10.1 through 10.1.58, and 9.0 through 9.0.121, as well as end-of-life releases such as 8.5 up to 8.5.100. The core technical deficiency lies within the TLS implementation layers, specifically impacting both the standard OpenSSL integration and the OpenSSL-FFM (Foreign Function Memory) variant. When a server is configured to use a Java keystore for managing SSL/TLS certificates, these implementations fail to properly process Certificate Revocation Lists or Online Certificate Status Protocol responses during the handshake phase. This means that if a client presents a certificate that has been revoked by its issuing Certification Authority due to compromise, key leakage, or policy violation, Apache Tomcat will still accept it as valid and proceed with establishing an encrypted session.
From a technical perspective, this issue stems from how Java-based TLS implementations interact with underlying native libraries like OpenSSL. In many configurations, the application server relies on the keystore for certificate storage but may delegate validation logic to the native provider without correctly passing revocation status data or ignoring it entirely due to configuration defaults that prioritize performance over strict compliance. The absence of a proper check allows an attacker who possesses a revoked certificate to authenticate as a legitimate entity. This bypasses one of the primary mechanisms designed to detect compromised credentials in public key infrastructure systems. While some clients might perform their own revocation checks, relying solely on client-side validation is insufficient because many enterprise environments and automated services do not enforce strict revocation checking by default or may be configured to ignore errors for compatibility reasons.
The operational impact of this vulnerability is significant, particularly in high-security environments where mutual TLS authentication is employed. An attacker with access to a revoked certificate can impersonate authorized users, systems, or microservices within the network architecture. This could lead to unauthorized data exfiltration, injection of malicious payloads into secure channels, or lateral movement across trusted segments that rely on certificate-based identity verification. Since Tomcat serves as a web server and servlet container for numerous enterprise applications, compromising its TLS validation integrity undermines the confidentiality and authenticity guarantees provided by HTTPS connections. Attackers could exploit this to conduct man-in-the-middle attacks more effectively if they can inject their own revoked certificates into traffic flows or use stolen credentials that have been formally deprovisioned but remain technically accepted by the server.
This vulnerability maps directly to CWE-295, which describes Improper Certificate Validation, and specifically relates to the failure to check revocation status. In terms of offensive security frameworks, it aligns with MITRE ATT&CK technique T1078, Valid Accounts, as an attacker can leverage previously valid but now revoked credentials to maintain access or escalate privileges without detection by standard certificate validation mechanisms. The risk is further exacerbated in environments where automated systems do not perform rigorous client-side revocation checks, assuming the server will enforce strict compliance.
To mitigate this risk, organizations must upgrade Apache Tomcat immediately to version 11.0.26, 10.1.59, or 9.0.122, which contain the necessary patches to restore proper certificate revocation checking behavior when using keystores. For environments where upgrading is not immediately feasible, administrators should consider disabling TLS configurations that rely on OpenSSL implementations if possible and switching to JSSE-based providers with explicit revocation policies enabled via JVM arguments such as com.sun.net.ssl.checkRevocation=true. Additionally, implementing network-level controls like firewalls or intrusion detection systems can help monitor for connections using revoked certificates by inspecting certificate fingerprints in transit, although this is a compensating control rather than a fix for the underlying application flaw. Regular audits of TLS configurations and ensuring that all components in the trust chain are up to date are essential practices to maintain robust security posture against such validation bypasses.