CVE-2022-32296 in Linux
Summary
by MITRE • 06/06/2022
The Linux kernel before 5.17.9 allows TCP servers to identify clients by observing what source ports are used.
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Analysis
by VulDB Data Team • 06/08/2022
This vulnerability exists in the Linux kernel version 5.17.9 and earlier, where TCP servers can potentially identify clients by monitoring the source port allocation patterns used by the kernel. The flaw stems from the predictable nature of how the kernel assigns source ports during TCP connection establishment, creating a fingerprinting opportunity for network observers. This behavior violates fundamental security principles by exposing information about client network characteristics through seemingly innocuous network traffic analysis. The vulnerability is classified under CWE-200 as exposure of sensitive information and aligns with ATT&CK technique T1592 for reconnaissance through network scanning and analysis.
The technical implementation of this vulnerability involves the kernel's port allocation algorithm which uses predictable patterns when selecting source ports for outgoing TCP connections. When a client establishes a TCP connection to a server, the kernel assigns a source port from its ephemeral port range, and the specific pattern of port selection can reveal information about the client's operating system, network configuration, or even specific client software characteristics. Network-based attackers can observe these port selection patterns over time and correlate them with other network behavior to build profiles of specific clients or identify network activities.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables sophisticated reconnaissance attacks that can be combined with other techniques to build comprehensive client profiles. Attackers can use this information to identify specific client systems, track user activities across networks, or correlate client behavior with known vulnerabilities in specific operating system versions. The vulnerability particularly affects server-side applications that process large volumes of connections or those that maintain long-term client sessions, as the cumulative observation of port selection patterns provides increasingly accurate client identification capabilities.
Mitigation strategies for this vulnerability include upgrading to Linux kernel version 5.17.9 or later, where the kernel implements improved port allocation algorithms that reduce predictability. System administrators should also consider implementing network-level protections such as source port randomization, network address translation, or firewall rules that limit the exposure of port selection patterns. Additionally, applications should be designed to minimize reliance on predictable port behavior and implement proper connection management techniques that reduce the information leakage potential. Organizations should conduct regular security assessments to identify systems running vulnerable kernel versions and ensure timely patch deployment to maintain network security posture.