CVE-2019-19055 in Linux
Summary
by MITRE
A memory leak in the nl80211_get_ftm_responder_stats() function in net/wireless/nl80211.c in the Linux kernel through 5.3.11 allows attackers to cause a denial of service (memory consumption) by triggering nl80211hdr_put() failures, aka CID-1399c59fa929.
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Analysis
by VulDB Data Team • 08/10/2025
The vulnerability CVE-2019-19055 represents a critical memory leak condition within the Linux kernel's wireless subsystem, specifically affecting versions through 5.3.11. This issue resides in the nl80211_get_ftm_responder_stats() function located in net/wireless/nl80211.c, which handles IEEE 802.11 Fine Timing Measurement (FTM) responder statistics collection. The flaw manifests when the nl80211hdr_put() function fails during packet header construction, leading to improper memory deallocation and subsequent resource exhaustion. The vulnerability is particularly concerning as it operates at the kernel level, where memory management directly impacts system stability and availability. Attackers can exploit this by crafting malicious wireless frames that trigger the problematic code path, causing the kernel to repeatedly allocate memory without proper cleanup, ultimately consuming available system resources and leading to denial of service conditions.
The technical implementation of this vulnerability demonstrates a classic memory management flaw where error handling paths fail to release allocated resources properly. When nl80211hdr_put() encounters a failure condition during header construction for FTM responder statistics, the code path does not execute the necessary cleanup routines that would normally free previously allocated memory buffers. This pattern aligns with CWE-401, which specifically addresses memory leaks in software systems. The vulnerability operates through the wireless subsystem's netlink interface, where user-space applications communicate with kernel-space drivers to retrieve wireless statistics. The FTM responder functionality is typically used in wireless positioning systems and network performance monitoring, making this attack vector particularly relevant in environments where wireless infrastructure is heavily utilized. The memory leak occurs incrementally with each failed header put operation, creating a gradual but steady consumption of system memory that can eventually render the device unusable.
The operational impact of CVE-2019-19055 extends beyond simple resource exhaustion, as it can affect the stability and availability of wireless network infrastructure. Systems running vulnerable kernel versions may experience progressive performance degradation, system crashes, or complete unresponsiveness when subjected to sustained attack conditions. This vulnerability is particularly dangerous in enterprise environments where wireless access points, routers, and network monitoring systems may be continuously targeted by malicious actors seeking to disrupt services. The attack requires relatively simple conditions to trigger, as it only necessitates sending malformed wireless frames that cause the nl80211hdr_put() function to fail, making it an attractive target for automated exploitation. Network administrators may find it challenging to detect this attack since it appears as normal wireless traffic, but gradually consumes system resources over time. The vulnerability affects a broad range of devices including wireless routers, access points, and embedded systems that rely on the Linux kernel's wireless subsystem for their network functionality.
Mitigation strategies for CVE-2019-19055 primarily focus on immediate kernel updates and system hardening measures. The most effective approach involves upgrading to kernel versions 5.3.12 or later, where the memory leak has been addressed through proper error handling and resource cleanup. Organizations should prioritize patching critical infrastructure devices and implementing automated update mechanisms to prevent exploitation. Network segmentation and monitoring can help detect unusual memory consumption patterns that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1499.004, which covers Network Denial of Service attacks, and T1071.004, covering application layer protocols, since it specifically targets wireless network protocols. Additional mitigations include implementing wireless intrusion detection systems that can identify malformed frames targeting this specific vulnerability, configuring rate limiting on wireless traffic, and monitoring system memory usage for abnormal patterns. System administrators should also consider implementing network access controls to limit wireless frame transmission from untrusted sources and establish baseline memory usage metrics to quickly identify potential exploitation attempts. The vulnerability highlights the importance of proper error handling in kernel-space code and underscores the need for comprehensive testing of edge cases in wireless protocol implementations.