CVE-2018-15317 in BIG-IP
Summary
by MITRE
In BIG-IP 14.0.0-14.0.0.2, 13.0.0-13.1.0.7, 12.1.0-12.1.3.5, 11.6.0-11.6.3.2, or 11.2.1-11.5.6, an attacker sending specially crafted SSL records to a SSL Virtual Server will cause corruption in the SSL data structures leading to intermittent decrypt BAD_RECORD_MAC errors. Clients will be unable to access the application load balanced by a virtual server with an SSL profile until tmm is restarted.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability identified as CVE-2018-15317 represents a critical flaw in F5 Networks BIG-IP application delivery controllers affecting multiple versions across different major releases. This issue manifests when specially crafted SSL records are transmitted to SSL Virtual Servers, creating a condition where the underlying SSL data structures become corrupted. The vulnerability operates at the SSL protocol level within the BIG-IP system's traffic management module, specifically impacting how the system processes incoming encrypted traffic. The flaw demonstrates characteristics consistent with CWE-129, which addresses improper validation of array indices and other bounds checking issues that can lead to memory corruption. From an operational perspective, this vulnerability creates a persistent disruption to service availability as clients attempting to establish SSL connections encounter intermittent BAD_RECORD_MAC errors that prevent successful decryption of traffic. The impact extends beyond simple connection failures to create a complete service outage for applications that rely on SSL termination through the affected virtual servers.
The technical execution of this vulnerability involves an attacker manipulating SSL protocol records in a manner that exploits memory corruption within the BIG-IP system's SSL processing engine. When the system encounters these malformed records, the SSL data structures become corrupted in a way that causes the traffic management module to fail in properly decrypting subsequent legitimate SSL traffic. This corruption specifically affects the record layer processing within the SSL implementation, causing the system to generate BAD_RECORD_MAC errors that indicate cryptographic integrity failures. The vulnerability's exploitation pattern aligns with ATT&CK technique T1071.004, which covers application layer protocol traffic shaping and manipulation. The issue demonstrates how protocol-level flaws can be leveraged to create denial-of-service conditions that require manual intervention to resolve. The fact that the problem requires a restart of the tmm (traffic management module) process indicates that the corruption affects core system memory structures rather than just application-level state, making this a particularly severe vulnerability that can persist until system reboot.
The operational impact of CVE-2018-15317 extends beyond immediate service disruption to create cascading effects in environments that depend on high availability and continuous access to SSL-terminated applications. Organizations using affected BIG-IP versions face the risk of extended downtime as the system becomes unable to process SSL traffic until manual intervention occurs through service restart procedures. This vulnerability particularly affects load-balanced environments where multiple clients may be simultaneously impacted, creating potential for widespread service degradation across applications that rely on SSL termination. The intermittent nature of the BAD_RECORD_MAC errors means that administrators may not immediately recognize the underlying corruption issue, leading to extended troubleshooting periods and potential misdiagnosis of the root cause. From a security perspective, this vulnerability represents a significant risk in production environments where service availability is critical, as the requirement for manual tmm restarts creates operational overhead and potential for service interruption during maintenance windows. The vulnerability's presence in multiple major versions of the BIG-IP platform indicates that it represents a fundamental flaw in the SSL processing implementation that was not adequately addressed through patching cycles, making organizations across different release branches equally vulnerable. Mitigation strategies should include immediate implementation of vendor patches, network-level monitoring for suspicious SSL traffic patterns, and preparation of emergency restart procedures for affected systems.