CVE-2021-3588 in BlueZ
Summary
by MITRE • 06/10/2021
The cli_feat_read_cb() function in src/gatt-database.c does not perform bounds checks on the 'offset' variable before using it as an index into an array for reading.
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Analysis
by VulDB Data Team • 06/13/2021
The vulnerability identified as CVE-2021-3588 resides within the Bluetooth GATT (Generic Attribute Profile) database implementation in a popular Bluetooth stack library. This flaw exists in the cli_feat_read_cb() function located in the src/gatt-database.c source file, representing a classic buffer over-read condition that can lead to arbitrary code execution or system instability. The issue manifests when the function processes incoming GATT read requests without properly validating the offset parameter before utilizing it as an array index. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, which is a well-documented weakness that can result in memory corruption and potential privilege escalation. The affected system components typically include Bluetooth low energy (BLE) implementations that handle GATT characteristic reads, making this particularly concerning for IoT devices, mobile applications, and embedded systems that rely on Bluetooth communication protocols.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious GATT read request containing an oversized offset value that exceeds the bounds of the target array. When the cli_feat_read_cb() function processes this request, it directly uses the unvalidated offset as an index into a data structure without performing necessary bounds checking. This allows the function to access memory locations outside the intended array boundaries, potentially reading from or writing to adjacent memory regions. The operational impact of this vulnerability extends beyond simple memory corruption, as it can enable attackers to extract sensitive information from memory, cause application crashes, or in more sophisticated scenarios, potentially lead to remote code execution. The ATT&CK framework categorizes this as a Memory Injection technique under the T1055 category, specifically targeting the exploitation of memory corruption vulnerabilities in system libraries. The vulnerability is particularly dangerous in environments where Bluetooth services are exposed to untrusted networks or devices, as it can be exploited through standard GATT read operations without requiring elevated privileges.
Mitigation strategies for CVE-2021-3588 should focus on immediate code-level fixes and broader architectural improvements. The primary remediation involves implementing proper bounds checking within the cli_feat_read_cb() function to validate the offset parameter before array access, ensuring that the offset value falls within the valid range of the target array. This can be achieved through defensive programming practices such as validating input parameters against array dimensions and implementing proper error handling for out-of-bounds conditions. Organizations should also consider applying patches from the software vendors immediately, as this vulnerability affects widely used Bluetooth stack implementations. Network segmentation and access controls can provide additional layers of defense by limiting exposure of Bluetooth services to trusted networks only. Security monitoring should include detection of anomalous GATT read requests with suspicious offset values, and system administrators should implement regular vulnerability assessments targeting Bluetooth implementations. The fix aligns with industry best practices outlined in the OWASP Secure Coding Guidelines and follows the principle of least privilege by ensuring that all external inputs are properly validated before processing. Regular security updates and code reviews should be implemented to prevent similar vulnerabilities in future development cycles, particularly focusing on memory safety in network-facing components that handle user-provided data.