CVE-2018-16855 in Recursor
Summary
by MITRE
An issue has been found in PowerDNS Recursor before version 4.1.8 where a remote attacker sending a DNS query can trigger an out-of-bounds memory read while computing the hash of the query for a packet cache lookup, possibly leading to a crash.
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Analysis
by VulDB Data Team • 06/12/2023
The vulnerability identified as CVE-2018-16855 represents a critical memory safety issue within the PowerDNS Recursor software ecosystem. This flaw exists in versions prior to 4.1.8 and specifically targets the packet cache implementation mechanism. The vulnerability manifests when a remote attacker crafts and sends a specially formatted DNS query to the affected recursor service. The attack vector exploits a fundamental flaw in how the software handles hash computation for packet cache lookups, creating a scenario where the application attempts to access memory locations outside the bounds of allocated buffers.
The technical nature of this vulnerability stems from improper bounds checking during hash calculation operations within the DNS query processing pipeline. When the recursor receives a malformed or specially crafted query, the hash function responsible for determining cache lookup locations fails to validate input parameters properly. This results in an out-of-bounds memory read condition that can cause the application to crash or behave unpredictably. The flaw operates at the intersection of memory management and cryptographic hash operations, making it particularly dangerous as it can be triggered through normal network traffic without requiring authentication or elevated privileges.
From an operational impact perspective, this vulnerability creates significant risks for DNS infrastructure providers who rely on PowerDNS Recursor for their caching services. The remote exploit capability means that any system running vulnerable versions could be compromised through simple DNS query injection attacks. The resulting crashes can lead to denial of service conditions that disrupt legitimate DNS resolution services for end users. Network administrators face the challenge of maintaining service availability while patching systems, as the vulnerability can be exploited by attackers without detection, potentially leading to prolonged service degradation.
The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software implementations, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should implement immediate mitigation strategies including upgrading to PowerDNS Recursor version 4.1.8 or later, which contains the necessary patches to prevent the out-of-bounds memory access. Additionally, network monitoring should be enhanced to detect unusual query patterns that might indicate exploitation attempts, and rate limiting mechanisms can help reduce the impact of potential attacks. The fix addresses the root cause by implementing proper input validation and bounds checking within the hash computation functions, ensuring that memory access operations remain within allocated buffer boundaries and preventing the conditions that lead to the out-of-bounds read scenario.