CVE-2011-5056 in MaraDNS
Summary
by MITRE
The authoritative server in MaraDNS through 2.0.04 computes hash values for DNS data without restricting the ability to trigger hash collisions predictably, which might allow local users to cause a denial of service (CPU consumption) via crafted records in zone files, a different vulnerability than CVE-2012-0024.
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Analysis
by VulDB Data Team • 12/22/2024
The vulnerability identified as CVE-2011-5056 affects MaraDNS versions through 2.0.04 and represents a significant security flaw in the authoritative DNS server implementation. This issue stems from the server's hash table implementation which fails to properly handle hash collision scenarios, creating predictable conditions that can be exploited by malicious actors. The vulnerability specifically targets the hash computation mechanism used for DNS data storage and retrieval within the authoritative server component, making it a critical concern for DNS infrastructure security.
The technical flaw manifests in the hash function implementation where the server computes hash values for DNS records without adequate protection against predictable collision attacks. This weakness allows attackers to craft specific DNS zone records that will deliberately trigger hash collisions within the server's internal data structures. The vulnerability operates on the principle that when multiple hash values map to the same hash bucket, the data structure must handle these collisions, but the current implementation lacks proper collision resistance mechanisms. This design flaw enables an attacker to exploit the hash table's performance characteristics by creating records that force the system into worst-case collision scenarios, leading to exponential CPU consumption patterns.
From an operational impact perspective, this vulnerability creates a severe denial of service condition where local users can consume excessive CPU resources through carefully crafted DNS zone files. The attack vector requires only the ability to modify zone files on the target system, making it particularly dangerous as it can be executed by users with limited privileges. The resource exhaustion occurs because hash table lookups degrade from O(1) average case to O(n) worst-case performance when collisions are not properly managed, causing the server to spend excessive computational cycles processing the malicious records. This behavior aligns with the common security principle of algorithmic complexity attacks where predictable inputs can force worst-case performance scenarios.
The vulnerability demonstrates characteristics consistent with CWE-327 (Use of a Broken or Risky Cryptographic Algorithm) and CWE-400 (Uncontrolled Resource Consumption) categories, as the hash implementation fails to provide adequate cryptographic security properties and can be exploited to consume unlimited resources. The attack pattern follows typical denial of service methodologies documented in the MITRE ATT&CK framework under techniques related to resource exhaustion and algorithmic complexity attacks. Organizations using MaraDNS versions affected by this vulnerability face significant operational risks including service unavailability, increased system load, and potential cascading failures in DNS resolution across dependent services.
Mitigation strategies should focus on upgrading to patched versions of MaraDNS where the hash collision handling has been properly addressed. System administrators should also implement zone file validation controls to prevent the loading of suspicious records and consider implementing rate limiting mechanisms to reduce the impact of potential attacks. The fix typically involves implementing better hash function selection or adding collision resistance features to the existing hash table implementation. Additionally, monitoring for unusual CPU consumption patterns and implementing intrusion detection systems can help identify exploitation attempts before they cause significant service disruption. Organizations should also conduct regular security assessments of their DNS infrastructure to identify similar vulnerabilities in other authoritative server implementations.