CVE-2015-5311 in Authoritative Server
Summary
by MITRE
PowerDNS (aka pdns) Authoritative Server 3.4.4 before 3.4.7 allows remote attackers to cause a denial of service (assertion failure and server crash) via crafted query packets.
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Analysis
by VulDB Data Team • 11/23/2024
PowerDNS authoritative server version 3.4.4 and earlier contained a critical vulnerability that enabled remote attackers to execute denial of service attacks through carefully crafted query packets. This vulnerability manifested as an assertion failure within the server's processing logic, ultimately leading to complete server crashes and service unavailability. The flaw existed in the server's handling of malformed or specially constructed DNS query packets that bypassed normal validation procedures. When the authoritative server received such malicious packets, it would trigger an internal assertion that caused the process to terminate abruptly, resulting in a complete service outage for legitimate DNS queries.
The technical nature of this vulnerability stems from inadequate input validation within the DNS query processing pipeline. Attackers could construct specific packet formats that would cause the server to evaluate a condition that should never occur under normal operational circumstances, thereby triggering the assertion failure. This type of vulnerability falls under the category of improper input validation and can be classified as CWE-248, which represents an "Uncaught Exception" scenario where the system fails to properly handle exceptional conditions. The vulnerability's impact was particularly severe because it required no authentication or privileged access to exploit, making it a prime target for automated attack tools that could rapidly overwhelm DNS infrastructure.
The operational consequences of this vulnerability extended beyond simple service disruption, as it could be leveraged to create sustained denial of service conditions that would require manual intervention to restore normal operations. Organizations relying on PowerDNS authoritative servers for critical DNS infrastructure faced significant risks, as attackers could repeatedly exploit this weakness to maintain service outages. The vulnerability also highlighted the importance of robust error handling and defensive programming practices within DNS server implementations, as the assertion failure indicated a lack of proper exception recovery mechanisms. From an attacker perspective, this vulnerability mapped to ATT&CK technique T1499.004, which involves network denial of service attacks through exploitation of software vulnerabilities.
Mitigation strategies for CVE-2015-5311 required immediate patching to version 3.4.7 or later, which contained the necessary fixes to properly validate incoming DNS query packets and prevent the assertion failure condition. Organizations should have implemented network-level protections such as rate limiting and query filtering to reduce the impact of potential exploitation attempts. Additionally, monitoring systems should have been enhanced to detect unusual patterns of server crashes or restarts that might indicate exploitation attempts. The vulnerability also underscored the importance of maintaining current security patches and conducting regular vulnerability assessments of critical infrastructure components. Organizations with multiple PowerDNS instances needed to ensure consistent patch deployment across all servers to prevent attackers from targeting the weakest link in their DNS infrastructure. The incident highlighted the necessity of implementing comprehensive incident response procedures for handling such critical vulnerabilities and the importance of maintaining detailed operational logs to track exploitation attempts and system behavior during attacks.