CVE-2016-7467 in BIG-IP APM
Summary
by MITRE
The TMM SSO plugin in F5 BIG-IP APM 12.0.0 - 12.1.1, 11.6.0 - 11.6.1 HF1, 11.5.4 - 11.5.4 HF2, when configured as a SAML Identity Provider with a Service Provider (SP) connector, might allow traffic to be disrupted or failover initiated when a malformed, signed SAML authentication request from an authenticated user is sent via the SP connector.
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Analysis
by VulDB Data Team • 11/28/2022
The vulnerability identified as CVE-2016-7467 affects the TMM SSO plugin within F5 BIG-IP APM systems, specifically targeting versions ranging from 12.0.0 through 12.1.1 and various 11.x releases with their respective hotfixes. This issue manifests when the system is configured as a SAML Identity Provider with a Service Provider connector, creating a specific attack surface where malformed SAML authentication requests can cause operational disruptions. The flaw represents a significant concern for organizations relying on F5 BIG-IP APM for application access management and single sign-on functionality, as it directly impacts the availability and reliability of authentication services.
The technical root cause of this vulnerability lies in the insufficient validation of SAML authentication requests within the TMM SSO plugin's processing pipeline. When a malformed, yet signed SAML request is received through the SP connector, the system fails to properly handle the malformed data structure, leading to unexpected behavior in the traffic processing mechanisms. This improper handling can trigger cascading failures that disrupt normal traffic flow or initiate unintended failover operations within the load balancing infrastructure. The vulnerability specifically exploits the difference between signed and unsigned request handling, where the signature validation process does not adequately account for malformed request structures that could still pass initial signature verification while containing structural inconsistencies that cause the backend processing to fail.
The operational impact of CVE-2016-7467 extends beyond simple service disruption to potentially compromise the overall availability and stability of critical application access infrastructure. Organizations utilizing F5 BIG-IP APM for enterprise authentication may experience unexpected traffic disruptions that could affect user access to business applications, leading to productivity losses and potential revenue impacts. The failover initiation capability means that legitimate authentication traffic could inadvertently trigger redundant system operations, consuming additional resources and potentially causing cascading failures across interconnected systems. This vulnerability particularly affects environments where high availability and consistent authentication service delivery are critical requirements, as the disruption could occur without clear indication of the underlying cause.
Mitigation strategies for this vulnerability should prioritize immediate implementation of F5's official security patches and hotfixes released for the affected versions. Organizations should also implement network-level monitoring to detect anomalous SAML request patterns that might indicate exploitation attempts, leveraging intrusion detection systems to identify malformed requests before they reach the vulnerable components. Configuration hardening measures including stricter SAML request validation rules and enhanced logging of authentication events can help detect and prevent exploitation. The vulnerability aligns with CWE-20, which addresses "Improper Input Validation," and represents a specific implementation weakness in the SAML processing stack that could be exploited to cause denial of service conditions. Security teams should also consider implementing rate limiting and request validation mechanisms at the network perimeter to reduce the attack surface and provide additional defense-in-depth measures against this specific class of vulnerability.