CVE-2025-53506 is a high-severity vulnerability affecting Apache Tomcat, specifically related to uncontrolled resource consumption. This vulnerability allows HTTP/2 clients that do not acknowledge the initial settings frame, which reduces the maximum permitted concurrent streams, to exploit the system. The severity is rated at 7.5 on the CVSS scale, indicating a significant risk to organizations using affected versions of this widely deployed application server.
The impact of this vulnerability can lead to service disruption or denial of service (DoS). Apache Tomcat versions from 11.0.0-M1 through 11.0.8, 10.1.0-M1 through 10.1.42, and 9.0.0.M1 through 9.0.106 are known to be affected. Additionally, the end-of-life (EOL) versions from 8.5.0 through 8.5.100 may also be susceptible. Organizations utilizing these versions should prioritize immediate remediation to mitigate potential exploitation.
Apache has recommended users upgrade to version 11.0.9, 10.1.43, or 9.0.107, which include patches that address this critical issue. Given the high impact and the potential for exploitation, organizations should prioritize patching these vulnerabilities immediately.
The urgency for defenders is clear. Organizations must assess their current Tomcat deployments, identify vulnerable versions, and implement the necessary upgrades without delay to protect their systems from potential resource exhaustion attacks.
Vulnerability Details
This vulnerability allows uncontrolled resource consumption due to the failure of an HTTP/2 client to acknowledge essential settings. The CVSS score of 7.5 indicates a high severity level, which necessitates immediate attention. The affected products are various versions of Apache Tomcat, including 11.0.0-M1 through 11.0.8, 10.1.0-M1 through 10.1.42, and 9.0.0.M1 through 9.0.106. The EOL versions, while no longer supported, are also impacted.
Published on July 10, 2025, the vulnerability has been classified under CWE-400, which deals with resource exhaustion. Organizations should be aware of these classifications to properly assess their risk management strategies.
Technical Analysis
The root cause of this vulnerability lies in the improper handling of HTTP/2 protocol settings. When a client fails to acknowledge the initial settings frame, it can lead to excessive resource consumption, causing the server to become unresponsive. The attack vector is network-based, and the complexity of the attack is low, requiring no special privileges or user interaction.
With no privileges required and no user interaction necessary, this vulnerability poses a significant risk. The availability impact is high, as the server's resources can become exhausted, leading to service disruptions. Importantly, there is no confidentiality or integrity impact associated with this vulnerability.
Risk & Impact Analysis
Organizations that rely on Apache Tomcat for web applications face a real-world risk of service disruption due to this vulnerability. The blast radius could be significant, affecting all users attempting to access services hosted on the affected Tomcat instances. Given the potential for attackers to exploit this vulnerability easily, it is crucial for organizations to assess their exposure and implement necessary mitigations.
Based on the CVSS score of 7.5, organizations should prioritize remediation efforts. The potential impact on availability is high, and the urgency for patching cannot be overstated. Organizations should address this vulnerability in their priority patch cycle to prevent disruptions and maintain service availability.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of Apache Tomcat are affected by CVE-2025-53506: 11.0.0-M1 through 11.0.8, 10.1.0-M1 through 10.1.42, and 9.0.0.M1 through 9.0.106. Additionally, EOL versions from 8.5.0 through 8.5.100 are also known to be affected. Organizations should ensure they are on the fixed versions: 11.0.9, 10.1.43, or 9.0.107.
Mitigation & Remediation
To mitigate this vulnerability, organizations should upgrade to Apache Tomcat versions 11.0.9, 10.1.43, or 9.0.107, which have addressed the vulnerabilities. If immediate upgrades are not feasible, consider implementing configuration hardening and network controls to limit exposure, such as restricting access to trusted IPs and monitoring for unusual traffic patterns.
For further guidance on securing your applications, organizations can refer to our application security assessment services.
Detection Guidance
To detect potential exploitation of this vulnerability, organizations should monitor logs for unusual spikes in resource consumption. Behavioral anomalies, such as unexpected high traffic or failed connection attempts, may indicate attempted attacks. Implementing network signatures that flag large numbers of concurrent streams initiated from a single client can also provide early warning.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2025-53506 reflects a growing trend in resource exhaustion vulnerabilities, particularly in HTTP/2 implementations. This highlights the need for security teams to adopt robust testing practices during their development cycles to identify and mitigate such weaknesses early. Organizations should consider engaging in penetration testing to validate their defenses against these types of vulnerabilities.
Furthermore, organizations should develop a proactive incident response plan that includes detection and remediation of resource exhaustion attacks. Leveraging insights from this incident can inform better security practices and help prevent similar vulnerabilities in the future.
Security teams must remain vigilant in monitoring for vulnerabilities and reviewing their security posture regularly. This includes maintaining awareness of new threats and adjusting their strategies accordingly.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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