CVE-2007-3152 in c-ares
Summary
by MITRE
c-ares before 1.4.0 uses a predictable seed for the random number generator for the DNS Transaction ID field, which might allow remote attackers to spoof DNS responses by guessing the field value.
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Analysis
by VulDB Data Team • 07/30/2019
The vulnerability identified as CVE-2007-3152 affects the c-ares library version 1.4.0 and earlier, which is a widely used asynchronous DNS resolver library implementing the c-ares API. This library is integral to numerous applications and systems that require asynchronous DNS resolution capabilities, including web browsers, email clients, and network monitoring tools. The flaw resides in the library's implementation of the DNS Transaction ID field generation mechanism, which is critical for DNS security and integrity.
The technical flaw involves the use of a predictable seed value for the random number generator that generates DNS Transaction IDs. DNS Transaction IDs serve as a crucial security mechanism to prevent DNS spoofing attacks by ensuring that responses from authoritative servers can be correctly matched to the original queries sent by clients. When the seed value is predictable, attackers can compute the next Transaction ID value that will be generated, enabling them to forge DNS responses that appear legitimate to the client application. This vulnerability specifically targets the pseudo-random number generation algorithm implementation within the c-ares library, where the seed initialization does not incorporate sufficient entropy to ensure unpredictability.
The operational impact of this vulnerability is significant as it creates a pathway for remote attackers to conduct DNS spoofing attacks against systems using vulnerable c-ares implementations. An attacker positioned in the network path between a client and a DNS server can monitor DNS queries and predict the Transaction ID values used in subsequent responses. This allows them to inject false DNS records into the client's cache, potentially redirecting traffic to malicious servers, facilitating man-in-the-middle attacks, or enabling phishing operations. The vulnerability affects systems where applications rely on c-ares for DNS resolution, including but not limited to web browsers, email clients, and network infrastructure tools that depend on this library for asynchronous DNS operations.
This vulnerability aligns with CWE-330, which addresses the use of insufficiently random values, and represents a specific instance of weak random number generation that compromises network security. From an ATT&CK framework perspective, this vulnerability maps to techniques involving DNS tunneling and DNS cache poisoning, specifically T1071.004 for application layer protocol and T1566 for credential access through social engineering. The predictable nature of the Transaction ID generation creates a fundamental weakness in the DNS security model that can be exploited without requiring extensive network monitoring or sophisticated attack infrastructure. Organizations using vulnerable versions of c-ares should immediately upgrade to version 1.4.0 or later, which implements proper random number generation with adequate entropy sources, and consider implementing additional network-level protections such as DNSSEC validation to mitigate potential exploitation risks.