CVE-2018-12545 in Jetty
Summary
by MITRE
In Eclipse Jetty version 9.3.x and 9.4.x, the server is vulnerable to Denial of Service conditions if a remote client sends either large SETTINGs frames container containing many settings, or many small SETTINGs frames. The vulnerability is due to the additional CPU and memory allocations required to handle changed settings.
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Analysis
by VulDB Data Team • 08/08/2023
The vulnerability identified as CVE-2018-12545 affects Eclipse Jetty servers running versions 9.3.x and 9.4.x, representing a significant denial of service weakness that can be exploited through HTTP/2 protocol manipulation. This flaw specifically targets the server's handling of SETTINGS frames within the HTTP/2 communication layer, where malicious clients can exploit the server's resource allocation mechanisms to consume excessive computational resources. The vulnerability stems from insufficient validation and resource management when processing SETTINGS frames that contain either a large number of settings within a single frame or numerous small SETTINGS frames sent in sequence, creating a scenario where legitimate server operations become overwhelmed by resource-intensive processing requirements.
The technical root cause of this vulnerability lies in the inadequate bounds checking and resource allocation strategies employed by the Jetty server implementation when processing HTTP/2 SETTINGS frames. When a remote client sends either a single SETTINGS frame containing an excessive number of parameters or multiple small SETTINGS frames, the server must allocate additional CPU cycles and memory resources to parse and process these configuration changes. This processing overhead is not properly bounded, allowing an attacker to systematically consume server resources through carefully crafted requests that trigger excessive memory allocations and CPU utilization patterns. The vulnerability is classified under CWE-400 as an unchecked resource allocation, where the server fails to implement proper resource limits and validation mechanisms for incoming SETTINGS frame data.
The operational impact of this vulnerability extends beyond simple service disruption, as it can lead to complete server unresponsiveness and resource exhaustion across multiple system components. Attackers can leverage this weakness to consume significant amounts of server memory and CPU cycles, potentially causing cascading failures that affect other services running on the same infrastructure. The vulnerability is particularly dangerous in high-traffic environments where Jetty servers handle numerous concurrent connections, as the resource exhaustion can quickly propagate to affect the entire application stack. This type of denial of service attack operates at the protocol level, making it difficult to distinguish from legitimate traffic patterns and complicating detection and mitigation efforts.
Mitigation strategies for CVE-2018-12545 should focus on implementing proper resource limits and validation mechanisms within the HTTP/2 processing layer. Organizations should upgrade to patched versions of Eclipse Jetty that include proper bounds checking for SETTINGS frames and implement rate limiting mechanisms to prevent excessive SETTINGS frame processing. Network-level protections such as connection limits, frame size restrictions, and monitoring for unusual SETTINGS frame patterns can provide additional defense in depth. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and organizations should consider implementing intrusion detection systems that can identify suspicious patterns of SETTINGS frame processing. System administrators should also monitor server resource utilization and implement automated alerting for unusual CPU and memory consumption patterns that may indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to ensure proper implementation of these mitigations and to identify any potential bypasses or additional weaknesses in the server configuration.