CVE-2018-5532 in BIG-IP
Summary
by MITRE
On F5 BIG-IP 13.0.0, 12.1.0-12.1.2, 11.6.0-11.6.3.1, or 11.2.1-11.5.6 a domain name cached within the DNS Cache of TMM may continue to be resolved by the cache even after the parent server revokes the record, if the DNS Cache is receiving a stream of requests for the cached name.
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Analysis
by VulDB Data Team • 04/18/2023
The vulnerability identified as CVE-2018-5532 affects F5 BIG-IP appliances running specific versions including 13.0.0, 12.1.0 through 12.1.2, 11.6.0 through 11.6.3.1, and 11.2.1 through 11.5.6. This issue resides within the Traffic Management Microkernel (TMM) component's DNS caching mechanism, representing a significant security concern for network infrastructure deployments. The flaw manifests when the DNS cache continues to serve stale records even after the authoritative DNS server has revoked or updated the corresponding domain name record, creating a persistent cache inconsistency that can be exploited by malicious actors.
The technical root cause of this vulnerability stems from improper cache invalidation mechanisms within the TMM's DNS resolution process. When a domain name is cached, the system should properly monitor for updates or revocations from the parent DNS server and invalidate the cached record accordingly. However, in affected versions, the cache maintains its resolved records for extended periods regardless of server-side changes, particularly when the cache receives continuous streams of requests for the same name. This behavior violates fundamental DNS cache management principles and creates a window where cached data becomes outdated while still being actively served to clients. The vulnerability operates under CWE-200, which addresses information exposure, and specifically relates to improper handling of cached DNS records, making it a critical concern for network security operations.
The operational impact of this vulnerability extends beyond simple caching issues to potentially enable sophisticated attack vectors including cache poisoning, man-in-the-middle attacks, and service disruption scenarios. Attackers could exploit this weakness by first obtaining legitimate cached records and then manipulating the DNS environment to cause clients to receive stale information that appears valid. The persistent nature of the cached data means that even after the authoritative server has updated or revoked records, clients may continue receiving the compromised cached responses, creating a potential attack surface for credential theft, data interception, or service redirection attacks. This vulnerability directly aligns with ATT&CK technique T1071.004 for application layer protocol manipulation and T1566 for credential harvesting through network-based attacks.
Organizations affected by CVE-2018-5532 should immediately implement mitigations including applying the latest F5 security patches and updates, configuring DNS cache timeout values to more aggressive intervals, and implementing additional monitoring for anomalous DNS resolution patterns. Network administrators should also consider implementing DNS cache monitoring tools that can detect when cached records are being served beyond their intended validity periods. The recommended approach involves deploying the F5 security patches that address the specific cache invalidation logic, while simultaneously configuring the appliance to enforce stricter DNS cache behavior. Additionally, implementing network segmentation and access controls around DNS infrastructure can help limit the potential impact of any exploitation attempts. Regular security audits should verify that DNS cache configurations align with security best practices, ensuring that cached records are properly validated against authoritative sources before being served to network clients.