CVE-2019-2033 in Android
Summary
by MITRE
In create_hdr of dnssd_clientstub.c, there is a possible use after free. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android. Versions: Android-9. Android ID: A-121327565.
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Analysis
by VulDB Data Team • 05/31/2020
The vulnerability identified as CVE-2019-2033 resides within the dnssd_clientstub.c component of Android's networking stack, specifically in the create_hdr function where a use-after-free condition occurs. This flaw represents a critical security weakness that can be exploited to achieve local privilege escalation without requiring any additional execution privileges or user interaction. The vulnerability is particularly concerning as it exists within the core DNS service discovery client stub implementation that handles network service resolution operations. The use-after-free condition arises when memory allocated for DNS header structures is freed but subsequent operations attempt to access that same memory region, potentially allowing malicious code to manipulate the freed memory contents or redirect execution flow.
The technical exploitation of this vulnerability leverages the fundamental principle of memory management errors where freed memory blocks are accessed after deallocation, creating opportunities for arbitrary code execution. This type of vulnerability falls under CWE-416, which specifically addresses the use of freed memory condition, and aligns with ATT&CK technique T1068 which covers local privilege escalation through system-level vulnerabilities. The flaw occurs in the context of Android's network service discovery mechanism, which is integral to device functionality including Wi-Fi direct connections, service discovery, and network browsing operations. When the create_hdr function processes DNS service records, it may prematurely free memory structures while other processes continue to reference them, creating a window of opportunity for exploitation.
The operational impact of CVE-2019-2033 extends beyond simple privilege escalation as it can potentially enable attackers to gain elevated system privileges that would otherwise require physical access or prior compromise. This vulnerability affects Android 9.0 systems and represents a significant concern for device security since it requires no user interaction for exploitation, making it particularly dangerous in environments where devices may be left unattended or where automated attacks could be deployed. The lack of user interaction requirements means that malicious actors could potentially exploit this vulnerability remotely through network-based attacks or through compromised applications that leverage the affected networking components. The vulnerability's presence in the dnssd_clientstub component indicates that it impacts the core service discovery functionality that many applications and system components depend upon, amplifying the potential attack surface and impact scope.
Mitigation strategies for CVE-2019-2033 should focus on immediate patch deployment through official Android security updates, as the vulnerability has been addressed in subsequent Android releases. System administrators and device manufacturers should prioritize applying security patches to affected Android 9.0 devices to prevent exploitation. Additional defensive measures include implementing network segmentation to limit access to services that might trigger the vulnerable code paths, monitoring for unusual network service discovery activity, and applying application sandboxing techniques to limit potential exploitation impact. The vulnerability demonstrates the importance of memory safety practices in system-level code and reinforces the need for comprehensive code review processes that specifically target memory management patterns. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to make exploitation more difficult, though these measures provide only partial protection against well-crafted use-after-free attacks. Regular security assessments of networking components and service discovery mechanisms should be conducted to identify similar vulnerabilities in other system components that may present comparable risks.