CVE-2023-21186 in Android
Summary
by MITRE • 06/28/2023
In LogResponse of Dns.cpp, there is a possible out of bounds read due to a missing bounds check. This could lead to remote denial of service with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-13Android ID: A-261079188
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2023-21186 resides within the DNS response handling mechanism of Android 13 systems, specifically within the Dns.cpp file where the LogResponse function processes incoming DNS queries. This flaw represents a classic out-of-bounds read condition that occurs when the system fails to validate the boundaries of data structures before accessing them. The missing bounds check creates an opportunity for malicious actors to craft specially formatted DNS responses that trigger memory access violations. According to the Android security advisory, this vulnerability affects the core DNS resolution process and can be exploited remotely without requiring any additional privileges or user interaction, making it particularly concerning for network-based attacks.
The technical implementation of this vulnerability stems from inadequate input validation within the DNS response parsing logic. When the LogResponse function processes DNS packets, it assumes that all incoming data conforms to expected formats and sizes without performing proper boundary verification. This allows an attacker to send malformed DNS responses that cause the system to read memory locations beyond the allocated buffer boundaries. The vulnerability manifests as a remote denial of service condition where the system becomes unresponsive or crashes upon encountering the malformed data. This behavior aligns with CWE-129, which describes improper validation of array index values, and specifically relates to the broader category of buffer over-read conditions that can lead to system instability.
From an operational impact perspective, this vulnerability compromises the availability of DNS resolution services on affected Android devices, potentially disrupting network connectivity and application functionality that depends on proper DNS operations. The remote exploitation capability means that attackers can target devices without physical access or user interaction, making it a significant threat vector for network-based attacks. The lack of privilege requirements for exploitation further amplifies the risk, as it eliminates the need for elevated access rights that would typically be required for more sophisticated attacks. This vulnerability directly impacts the Android operating system's core networking capabilities and can be leveraged to create persistent denial of service conditions that affect device usability and network communication.
The mitigation strategies for this vulnerability primarily involve applying the latest security patches provided by Google through the Android security updates. Organizations and users should prioritize immediate deployment of the patched Android 13 system images that contain the fixed DNS response handling logic. The fix typically involves implementing proper bounds checking mechanisms within the LogResponse function to validate buffer boundaries before any memory access operations occur. Additionally, network administrators should consider implementing DNS filtering mechanisms that can detect and block malformed DNS responses before they reach vulnerable Android devices. This vulnerability demonstrates the importance of input validation in network protocols and aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through manipulation of network traffic. The security community should also monitor for similar patterns in other network protocol implementations that might exhibit similar boundary checking vulnerabilities.