CVE-2019-9501 in wl WiFi Driver
Summary
by MITRE
The Broadcom wl WiFi driver is vulnerable to a heap buffer overflow. By supplying a vendor information element with a data length larger than 32 bytes, a heap buffer overflow is triggered in wlc_wpa_sup_eapol. In the worst case scenario, by sending specially-crafted WiFi packets, a remote, unauthenticated attacker may be able to execute arbitrary code on a vulnerable system. More typically, this vulnerability will result in denial-of-service conditions.
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Analysis
by VulDB Data Team • 03/28/2024
The vulnerability identified as CVE-2019-9501 affects the Broadcom wl WiFi driver implementation, representing a critical heap buffer overflow condition that resides within the wireless networking stack of affected systems. This flaw specifically manifests in the wlc_wpa_sup_eapol function where insufficient bounds checking allows malicious data to overwrite adjacent memory regions. The vulnerability is triggered when processing vendor information elements that exceed the expected 32-byte limit, creating a scenario where attacker-controlled data can corrupt heap memory structures. The root cause aligns with CWE-121, heap-based buffer overflow, where the driver fails to validate input parameters before copying data into fixed-size buffers. This particular implementation flaw exists in the wireless access point authentication handling code path, making it accessible through standard IEEE 802.11 wireless frames that contain maliciously crafted vendor specific information elements.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions to encompass potential remote code execution capabilities. When an attacker sends specially crafted WiFi packets containing vendor information elements larger than 32 bytes, the heap buffer overflow can be leveraged to overwrite critical memory locations including function pointers, return addresses, or other control data structures. This memory corruption can lead to arbitrary code execution under the privileges of the wireless driver process, which typically runs with elevated system privileges. The remote and unauthenticated nature of this attack vector makes it particularly dangerous as attackers can exploit the vulnerability without requiring physical access or prior authentication to the wireless network. The vulnerability affects systems where the Broadcom wl driver is in use, commonly found in enterprise wireless infrastructure, consumer routers, and embedded networking devices that implement Broadcom wireless chipsets. The ATT&CK framework categorizes this as a privilege escalation technique through software exploitation, potentially mapping to T1068 for locally executed code and T1203 for legitimate user privileges.
Mitigation strategies for CVE-2019-9501 should prioritize immediate patch deployment from Broadcom and affected vendors, as the vulnerability represents a high-severity threat to wireless network security. Network administrators should implement wireless intrusion detection systems that can identify and block malformed vendor information elements, while also considering network segmentation to limit the potential impact of exploitation. The recommended approach includes disabling unused wireless features, implementing proper firewall rules to restrict wireless traffic, and maintaining up-to-date wireless firmware across all affected devices. System monitoring should focus on detecting unusual memory allocation patterns or process behavior that might indicate exploitation attempts. Organizations should also consider implementing network access control measures that can identify and quarantine devices exhibiting suspicious wireless behavior patterns. The vulnerability demonstrates the critical importance of input validation in network protocol implementations and highlights the need for rigorous security testing of wireless driver components. Regular vulnerability assessments and penetration testing of wireless infrastructure should be conducted to identify similar buffer overflow conditions that may exist in other network stack components. Additionally, the security community should remain vigilant for similar vulnerabilities in other wireless driver implementations that may share similar code patterns or architectural flaws.