CVE-2016-9244 in BIG-IP Virtual Server
Summary
by MITRE
A BIG-IP virtual server configured with a Client SSL profile that has the non-default Session Tickets option enabled may leak up to 31 bytes of uninitialized memory. A remote attacker may exploit this vulnerability to obtain Secure Sockets Layer (SSL) session IDs from other sessions. It is possible that other data from uninitialized memory may be returned as well.
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Analysis
by VulDB Data Team • 07/07/2024
The vulnerability identified as CVE-2016-9244 affects F5 BIG-IP systems when a virtual server is configured with a Client SSL profile that has the non-default Session Tickets option enabled. This represents a critical information disclosure flaw that stems from improper memory management within the SSL implementation. The issue manifests when the system processes SSL session tickets, which are used to enable session resumption without requiring a full handshake process. When Session Tickets are enabled, the system should properly initialize memory structures before using them, but in this case, uninitialized memory values are being exposed to remote attackers.
The technical exploitation of this vulnerability occurs through the transmission of SSL session tickets between client and server during the SSL handshake process. When the BIG-IP system generates or processes these tickets, it fails to properly clear or initialize memory regions that contain session identifiers. This memory leakage exposes up to 31 bytes of uninitialized data that may contain sensitive session information including SSL session IDs, which are critical for maintaining secure connections. The vulnerability specifically impacts systems where the Session Tickets option is enabled but not set to its default configuration, making it a configuration-dependent issue that can be exploited remotely without authentication.
From an operational impact perspective, this vulnerability allows remote attackers to obtain SSL session IDs from other active sessions, potentially enabling session hijacking attacks or facilitating more sophisticated exploitation techniques. The exposure of uninitialized memory can reveal not only session identifiers but potentially other sensitive data that may be present in the uninitialized memory regions. This type of information disclosure can significantly weaken the security posture of affected systems by providing attackers with valuable session state information that could be used to impersonate legitimate users or gain unauthorized access to protected resources. The vulnerability affects the fundamental security mechanisms of SSL/TLS connections, undermining the confidentiality guarantees that these protocols are designed to provide.
The flaw aligns with CWE-248, which addresses "Uncaught Exception" and specifically relates to improper handling of uninitialized memory in cryptographic implementations. This vulnerability also maps to ATT&CK technique T1552.001, "Unsecured Credentials", as it exposes session identifiers that could be used to gain unauthorized access to systems. Organizations using F5 BIG-IP systems with Client SSL profiles and enabled Session Tickets should immediately apply the vendor-provided security patches or updates to remediate this issue. Alternative mitigations include disabling the Session Tickets option in Client SSL profiles when not strictly required, or implementing network-level controls to monitor and restrict SSL session ticket exchanges. The vulnerability demonstrates the importance of proper memory initialization in cryptographic implementations and highlights the need for comprehensive security testing of SSL/TLS protocol handling within application security frameworks.