CVE-2007-3153 in c-ares
Summary
by MITRE
The ares_init:randomize_key function in c-ares, on platforms other than Windows, uses a weak facility for producing a random number sequence (Unix rand), which makes it easier for remote attackers to spoof DNS responses by guessing certain values.
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Analysis
by VulDB Data Team • 09/03/2018
The vulnerability identified as CVE-2007-3153 resides within the c-ares library, a widely used asynchronous DNS resolution library that powers numerous applications and systems requiring network communication. This flaw specifically affects Unix-like platforms excluding Windows, where the ares_init:randomize_key function employs the weak Unix rand() function to generate random number sequences. The fundamental issue stems from the predictable nature of the rand() function's output, which operates on a simple linear congruential generator algorithm that produces sequences with easily discernible patterns and limited entropy. This weakness directly impacts the library's ability to generate secure random values necessary for DNS query identification and response validation mechanisms.
The technical exploitation of this vulnerability occurs through a sophisticated attack vector that leverages the predictability of the random number generation process. Remote attackers can analyze the sequence of values produced by the weak random number generator and subsequently predict the specific random values used by the DNS resolver for query identification. This predictability enables attackers to craft spoofed DNS responses that appear legitimate to the vulnerable system, as the attacker can guess the expected transaction ID or other random values used to correlate DNS queries with their corresponding responses. The attack typically involves monitoring DNS traffic to observe the random sequence patterns and then using this knowledge to inject malicious DNS records that will be accepted by the target system due to the predictable nature of the random values used in the DNS resolution process.
The operational impact of this vulnerability extends beyond simple DNS spoofing, as it fundamentally undermines the security assurances provided by DNS resolution mechanisms. When systems relying on c-ares for DNS resolution are compromised, attackers gain the ability to redirect network traffic to malicious destinations, potentially leading to man-in-the-middle attacks, phishing operations, or the compromise of sensitive network communications. The vulnerability affects a broad spectrum of applications and systems that utilize the c-ares library, including web browsers, email clients, network monitoring tools, and various server applications that depend on asynchronous DNS resolution. This widespread applicability makes the vulnerability particularly dangerous as it can potentially affect thousands of systems across different environments, from personal computers to enterprise network infrastructure.
The weakness in this vulnerability aligns with CWE-330, which addresses the use of insufficiently random values, and specifically relates to the improper implementation of random number generation in security-critical contexts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving DNS tunneling and spoofing operations that leverage predictable random values to bypass security controls. The attack surface is further expanded by the fact that the vulnerability is not limited to a single application but affects the underlying library that multiple systems depend upon, creating a cascading security risk across interconnected networks. Organizations should implement immediate mitigations including upgrading to patched versions of c-ares, implementing additional DNS security measures such as DNSSEC validation, and monitoring for suspicious DNS activity that may indicate exploitation attempts.
The remediation approach for CVE-2007-3153 requires systematic updates to the affected c-ares library implementations across all systems utilizing the vulnerable functionality. Security teams should prioritize patching efforts and verify that updated versions properly implement secure random number generation using cryptographically strong random number generators instead of the weak Unix rand() function. Additionally, organizations should consider implementing network-level security controls such as DNS filtering and monitoring solutions that can detect and prevent DNS spoofing attempts. The vulnerability demonstrates the critical importance of proper random number generation in security-sensitive applications and highlights how seemingly minor implementation details can create significant security weaknesses that compromise entire network infrastructures.