CVE-2016-2120 in Authoritative Server
Summary
by MITRE
An issue has been found in PowerDNS Authoritative Server versions up to and including 3.4.10, 4.0.1 allowing an authorized user to crash the server by inserting a specially crafted record in a zone under their control then sending a DNS query for that record. The issue is due to an integer overflow when checking if the content of the record matches the expected size, allowing an attacker to cause a read past the buffer boundary.
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Analysis
by VulDB Data Team • 06/04/2023
The vulnerability identified as CVE-2016-2120 represents a critical security flaw in PowerDNS Authoritative Server software that affects versions up to and including 3.4.10 and 4.0.1. This issue manifests as a denial of service condition that can be exploited by authorized users who possess the ability to modify DNS zone records within their controlled domains. The vulnerability stems from inadequate input validation mechanisms within the server's record processing logic, specifically when handling DNS record content validation. The flaw allows malicious actors with legitimate access privileges to manipulate the server's memory management through carefully crafted DNS records, potentially leading to complete service disruption.
The technical root cause of this vulnerability lies in an integer overflow condition that occurs during the validation process of DNS record content sizes. When the PowerDNS server processes a DNS query for a specially crafted record, the system performs size checks to ensure that the record content does not exceed predetermined boundaries. However, the implementation contains a flaw where integer overflow occurs during these size comparisons, causing the validation logic to fail catastrophically. This integer overflow condition specifically affects the boundary checking mechanism that determines whether the record content fits within allocated memory buffers. When the overflow occurs, it allows the system to attempt reading data beyond the allocated buffer boundaries, leading to unpredictable behavior and ultimately causing the server process to crash.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a significant threat to DNS infrastructure stability and availability. Attackers can leverage this flaw to perform targeted denial of service attacks against specific zones they control, potentially causing cascading effects if multiple authoritative servers are affected. The vulnerability is particularly concerning because it requires only authorized access to a zone, making it accessible to users with legitimate administrative privileges who may have been compromised or acting maliciously. This makes the attack surface broader than typical vulnerabilities that require external network access or authentication bypasses. The crash condition affects the entire server process, meaning that legitimate DNS queries for other zones may also be impacted during the recovery period, creating additional operational challenges for system administrators.
Mitigation strategies for CVE-2016-2120 should prioritize immediate software updates to versions that have addressed this integer overflow condition in the DNS record validation logic. Organizations should implement comprehensive monitoring of DNS server processes to detect unusual crash patterns or memory access violations that may indicate exploitation attempts. Network segmentation and access control measures should be reinforced to limit the scope of potential attacks, ensuring that unauthorized users cannot manipulate DNS records even if they gain access to the system. The vulnerability aligns with CWE-190, which describes integer overflow conditions, and represents a classic example of how memory safety issues can be exploited to cause system instability. From an adversarial perspective, this vulnerability would likely be categorized under ATT&CK technique T1499.004, which covers network disruption attacks, as the primary impact is service availability degradation through server crashes. System administrators should also consider implementing automated failover mechanisms and redundant DNS infrastructure to minimize the impact of such attacks on overall network availability and ensure continued service delivery during remediation efforts.