CVE-2020-22217 in c-ares
Summary
by MITRE • 08/22/2023
Buffer overflow vulnerability in c-ares before 1_16_1 thru 1_17_0 via function ares_parse_soa_reply in ares_parse_soa_reply.c.
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Analysis
by VulDB Data Team • 09/16/2023
The buffer overflow vulnerability identified as CVE-2020-22217 affects the c-ares library, a widely-used asynchronous DNS resolver library that is integral to numerous applications and systems requiring DNS resolution capabilities. This vulnerability specifically resides within the ares_parse_soa_reply function located in the ares_parse_soa_reply.c source file, making it a critical security flaw that could potentially compromise the stability and security of systems relying on this library. The affected versions span from c-ares before 1_16_1 through 1_17_0, indicating a substantial range of releases that may be vulnerable to exploitation.
The technical flaw manifests as a classic buffer overflow condition where the ares_parse_soa_reply function fails to properly validate input data length before copying it into a fixed-size buffer. This occurs during the parsing of SOA (Start of Authority) resource records in DNS responses, which are critical components in DNS zone transfers and authoritative server communications. When processing malformed or oversized SOA records, the function attempts to copy data beyond the allocated buffer boundaries, potentially overwriting adjacent memory locations and causing unpredictable behavior. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a direct violation of secure coding practices that require proper bounds checking before memory operations.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it could potentially enable remote code execution depending on the specific memory corruption patterns and the target system's memory layout. Attackers could craft malicious DNS responses containing oversized SOA records that trigger the buffer overflow when processed by applications using the vulnerable c-ares library. This exploitation vector poses significant risks to systems that rely on DNS resolution for critical operations, including web servers, network infrastructure, and applications that perform DNS lookups without proper input sanitization. The vulnerability affects any application or system that utilizes c-ares for DNS resolution, which includes major software products from companies like Google, Microsoft, and various open-source projects that depend on this library for network communications.
Mitigation strategies for CVE-2020-22217 primarily involve immediate patching of affected c-ares library versions to 1_16_1 or later, which contains the necessary fixes for the buffer overflow condition. System administrators should prioritize updating all applications and services that depend on c-ares to ensure they are using patched versions of the library. Additionally, network monitoring should be enhanced to detect unusual DNS traffic patterns that might indicate exploitation attempts, particularly focusing on SOA record responses that exceed normal size parameters. The vulnerability's characteristics align with ATT&CK technique T1071.004, which covers DNS protocol tunneling, as attackers might leverage DNS resolution vulnerabilities for command and control communications. Organizations should also implement input validation controls at the application level to reduce the attack surface and consider network segmentation to limit the potential impact of successful exploitation attempts.