CVE-2023-26464 in Log4j
Summary
by MITRE • 03/10/2023
** UNSUPPORTED WHEN ASSIGNED ** When using the Chainsaw or SocketAppender components with Log4j 1.x on JRE less than 1.7, an attacker that manages to cause a logging entry involving a specially-crafted (ie, deeply nested) hashmap or hashtable (depending on which logging component is in use) to be processed could exhaust the available memory in the virtual machine and achieve Denial of Service when the object is deserialized. This issue affects Apache Log4j before 2. Affected users are recommended to update to Log4j 2.x. NOTE: This vulnerability only affects products that are no longer supported by the maintainer.
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Analysis
by VulDB Data Team • 11/28/2024
This vulnerability exists within the Apache Log4j 1.x logging framework and specifically impacts systems utilizing the Chainsaw or SocketAppender components when running on Java Runtime Environments older than version 1.7. The flaw represents a denial of service condition that can be triggered through careful manipulation of serialized data structures during logging operations. The vulnerability is particularly concerning because it leverages the deserialization process to create memory exhaustion conditions that can completely disrupt application availability. When an attacker crafts specially designed hashmap or hashtable objects that are deeply nested, these structures can cause the virtual machine to consume excessive memory resources during the deserialization phase, ultimately leading to system crashes or unresponsiveness.
The technical mechanism behind this vulnerability stems from how Log4j 1.x handles object deserialization within its logging components. The Chainsaw and SocketAppender features are designed to transmit log data over network connections or process it through specialized logging tools, but they do not properly validate the depth or complexity of serialized objects. When a deeply nested hashmap or hashtable structure is processed through these components, the deserialization routine recursively traverses the object hierarchy without adequate safeguards against excessive nesting levels. This recursive traversal creates a memory consumption pattern that grows exponentially with each additional nesting level, eventually exhausting the available heap memory. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption vulnerability, specifically manifesting as a denial of service through resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system stability and availability. In enterprise environments where logging is critical for monitoring and debugging, an attacker could exploit this weakness to cause cascading failures across multiple applications that rely on the same logging infrastructure. The vulnerability is particularly dangerous in environments where automated systems or scripts continuously process log data, as these systems could be targeted to consume all available memory resources and render the entire logging infrastructure ineffective. The issue affects systems running on Java versions prior to 1.7 because older JVM implementations lack the memory management protections and stack overflow detection mechanisms that would prevent such recursive exploitation patterns.
Organizations affected by this vulnerability should prioritize immediate migration to Log4j 2.x, which contains comprehensive fixes for deserialization vulnerabilities and improved memory management controls. The recommended mitigation strategy involves not only updating the logging framework but also implementing proper input validation and sanitization for all logging operations that involve external data sources. System administrators should also consider implementing network segmentation and access controls to limit exposure of logging components to untrusted data sources. The ATT&CK framework categorizes this vulnerability under T1499.004 as a Network Denial of Service attack, where the attacker leverages application-specific weaknesses to exhaust system resources. Additionally, this vulnerability demonstrates the importance of keeping software components updated, as the issue only affects unsupported versions of Log4j, highlighting the critical need for maintaining current security patches and following software lifecycle management practices.