CVE-2017-15094 in Recursor
Summary
by MITRE
An issue has been found in the DNSSEC parsing code of PowerDNS Recursor from 4.0.0 up to and including 4.0.6 leading to a memory leak when parsing specially crafted DNSSEC ECDSA keys. These keys are only parsed when validation is enabled by setting dnssec to a value other than off or process-no-validate (default).
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Analysis
by VulDB Data Team • 02/02/2023
The vulnerability identified as CVE-2017-15094 represents a critical memory management flaw within the PowerDNS Recursor DNS server software. This issue specifically affects versions 4.0.0 through 4.0.6, where the DNSSEC parsing functionality contains a memory leak condition that can be triggered through carefully constructed DNSSEC ECDSA key data. The vulnerability operates within the context of DNS security validation mechanisms, which are essential for ensuring the authenticity and integrity of DNS responses in modern network infrastructures. The flaw manifests when the recursor processes DNSSEC validation requests and encounters specially crafted ECDSA keys, leading to progressive memory consumption that can ultimately degrade system performance or cause service disruption.
The technical implementation of this vulnerability stems from inadequate memory deallocation within the DNSSEC parsing code path. When the PowerDNS Recursor encounters DNSSEC ECDSA keys during validation processing, the memory allocated for key parsing operations is not properly freed, creating a memory leak condition that accumulates over time. This type of vulnerability falls under the CWE-401 category of "Improper Release of Memory Before Removing Last Reference" and represents a classic example of resource exhaustion through memory leaks. The operational impact is particularly concerning because DNSSEC validation is typically enabled in production environments to ensure secure DNS resolution, making this vulnerability exploitable in legitimate operational scenarios rather than requiring special attack conditions. The memory leak occurs specifically when the dnssec configuration parameter is set to values other than "off" or "process-no-validate", indicating that the vulnerability is directly tied to the activation of DNS security features.
The operational implications of CVE-2017-15094 extend beyond simple performance degradation to potential system instability and service availability issues. As the memory leak accumulates, system resources become increasingly constrained, potentially leading to process termination, system crashes, or denial of service conditions that affect DNS resolution for all clients served by the affected recursor. This vulnerability aligns with ATT&CK technique T1499.004 which involves resource exhaustion attacks targeting memory resources. The impact is particularly severe for high-traffic DNS environments where the recursor processes thousands of DNSSEC validation requests per second, as the memory leak would rapidly compound and reach critical levels. Network administrators must consider that this vulnerability can be exploited passively through normal DNS traffic patterns, as the malicious input does not require active exploitation but rather occurs during legitimate DNSSEC validation processing.
Mitigation strategies for CVE-2017-15094 focus on immediate software updates to versions beyond 4.0.6 where the memory leak has been addressed through proper memory deallocation routines. Organizations should implement comprehensive monitoring of system memory usage and DNS recursor performance metrics to detect early signs of memory exhaustion. The remediation process should include not only patching the software but also implementing resource limits and watchdog processes to prevent complete service failure. Additionally, organizations may consider temporarily disabling DNSSEC validation in environments where the vulnerability is actively exploited, though this reduces overall DNS security. The fix implemented in later versions demonstrates proper memory management practices and aligns with security best practices for handling cryptographic key processing in network services, ensuring that all allocated memory is properly released regardless of processing success or failure conditions.