CVE-2016-7074 in PowerDNS
Summary
by MITRE
An issue has been found in PowerDNS before 3.4.11 and 4.0.2, and PowerDNS recursor before 4.0.4, allowing an attacker in position of man-in-the-middle to alter the content of an AXFR because of insufficient validation of TSIG signatures. A missing check that the TSIG record is the last one, leading to the possibility of parsing records that are not covered by the TSIG signature.
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Analysis
by VulDB Data Team • 05/08/2023
The vulnerability described in CVE-2016-7074 represents a critical security flaw in PowerDNS software versions prior to 3.4.11 and 4.0.2, as well as PowerDNS recursor versions before 4.0.4. This issue specifically affects the handling of DNS zone transfers, particularly AXFR (Authoritative Zone Transfer) operations that utilize TSIG (Transaction Signature) for authentication and integrity verification. The flaw stems from an insufficient validation mechanism that fails to properly verify the positioning of TSIG records within DNS messages, creating a fundamental gap in the security model that could be exploited by attackers positioned in man-in-the-middle scenarios.
The technical root cause of this vulnerability lies in the improper parsing logic of DNS messages containing TSIG signatures. When a DNS server receives an AXFR request, it must validate the TSIG signature to ensure the integrity of the entire zone transfer. However, the vulnerable PowerDNS implementations failed to enforce a critical validation check that requires the TSIG record to appear as the final record in the DNS message. This omission allows an attacker to inject additional DNS records between the TSIG signature and the end of the message, effectively bypassing the signature verification mechanism. The attack exploits the fact that TSIG signatures only cover the data preceding the TSIG record itself, leaving any records that follow the signature unverified and potentially manipulable.
From an operational perspective, this vulnerability creates a significant risk for DNS infrastructure security, particularly in environments where DNS zone transfers occur between authoritative servers. The man-in-the-middle attack scenario is particularly dangerous because it allows an attacker to modify DNS records during the transfer process without detection. This could lead to various malicious activities including DNS cache poisoning, redirection of traffic to malicious servers, or disruption of network services. The impact extends beyond simple data manipulation as it undermines the fundamental trust model of DNS security, potentially allowing attackers to compromise entire domains or services that rely on proper DNS zone integrity.
The vulnerability aligns with CWE-200, which describes insufficient input validation, and specifically relates to CWE-310, which covers cryptographic issues including improper implementation of cryptographic protocols. From an ATT&CK framework perspective, this vulnerability maps to T1071.004, which covers DNS tunneling and manipulation, and T1566, which encompasses phishing and social engineering techniques that could exploit the compromised DNS infrastructure. Organizations using vulnerable PowerDNS versions face potential compromise of their entire DNS infrastructure, as the flaw allows attackers to manipulate authoritative zone data without detection. The security implications are particularly severe in environments where DNS serves as a critical infrastructure component for service discovery, load balancing, and network access control.
Mitigation strategies for this vulnerability require immediate patching of all affected PowerDNS installations to versions 3.4.11 and 4.0.2 for the main PowerDNS server, and 4.0.4 for the recursor component. Additionally, organizations should implement network-level monitoring to detect anomalous DNS traffic patterns that might indicate exploitation attempts. The fix implemented in these patched versions ensures proper validation of TSIG record positioning and enforces that all DNS records, including those that might be injected by attackers, are properly covered by the TSIG signature. Network administrators should also consider implementing additional security measures such as DNSSEC deployment, which provides additional layers of authentication and integrity protection beyond TSIG, and regular security auditing of DNS infrastructure to identify and remediate similar vulnerabilities.