CVE-2019-10191 in Resolver
Summary
by MITRE
A vulnerability was discovered in DNS resolver of knot resolver before version 4.1.0 which allows remote attackers to downgrade DNSSEC-secure domains to DNSSEC-insecure state, opening possibility of domain hijack using attacks against insecure DNS protocol.
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Analysis
by VulDB Data Team • 10/02/2024
The vulnerability identified as CVE-2019-10191 affects the knot resolver DNS implementation and represents a significant security flaw that undermines the integrity of DNSSEC validation mechanisms. This vulnerability specifically impacts versions prior to 4.1.0 of the knot resolver software, creating a pathway for remote attackers to manipulate DNS resolution behavior and potentially compromise domain security. The flaw operates at the intersection of DNS security protocols and resolver implementation, where proper validation of DNSSEC signatures can be circumvented through carefully crafted malicious responses.
The technical implementation of this vulnerability stems from improper handling of DNSSEC validation states during the resolution process. When a resolver encounters DNSSEC-secure domains, it should maintain the secure state throughout the resolution chain, but the flaw allows attackers to inject responses that cause the resolver to downgrade the security status from secure to insecure. This downgrade process typically occurs through manipulation of DNS response packets that contain authoritative data, causing the resolver to accept insecure responses from malicious actors while still maintaining a cached secure state for the domain. The vulnerability specifically relates to how the resolver processes and validates DNSSEC records during the resolution process, allowing attackers to exploit the state transition mechanism.
The operational impact of this vulnerability extends beyond simple DNS resolution issues and creates substantial risk for domain hijacking operations. When DNSSEC-secure domains are downgraded to insecure state, attackers can exploit the vulnerability to redirect traffic to malicious endpoints while the victim resolver continues to accept the malicious responses. This creates an environment where legitimate DNSSEC validation is bypassed, allowing attackers to perform cache poisoning attacks or redirect users to malicious sites without detection. The vulnerability essentially creates a backdoor where attackers can manipulate DNS resolution behavior, potentially compromising entire domains that were previously protected by DNSSEC validation. This type of attack falls under the broader category of DNS cache poisoning and can result in significant operational disruption and security breaches.
Mitigation strategies for CVE-2019-10191 focus primarily on updating to version 4.1.0 or later of the knot resolver software where the vulnerability has been patched. Organizations should also implement additional monitoring of DNS resolution behavior and establish detection mechanisms for unusual DNSSEC validation state transitions. Network administrators should consider implementing DNSSEC-aware monitoring tools that can detect when domains are being downgraded from secure to insecure states. The vulnerability aligns with CWE-200, which addresses information exposure, and represents a specific instance of improper information handling within DNSSEC validation processes. From an ATT&CK framework perspective, this vulnerability maps to techniques involving DNS cache poisoning and credential access through manipulation of DNS resolution processes. Organizations should also consider implementing additional security controls such as DNS query logging, response validation, and network segmentation to limit the potential impact of such attacks. The patch for this vulnerability specifically addresses the DNSSEC state transition handling and ensures that secure domains maintain their security status throughout the resolution process, preventing attackers from exploiting the downgrade mechanism.