CVE-2006-2076 in pdnsd
Summary
by MITRE
Memory leak in Paul Rombouts pdnsd before 1.2.4 allows remote attackers to cause a denial of service (memory consumption) via a DNS query with an unsupported (1) QTYPE or (2) QCLASS, as demonstrated by the OUSPG PROTOS DNS test suite.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability described in CVE-2006-2076 represents a critical memory management flaw in the pdnsd DNS proxy software developed by Paul Rombouts. This issue affects versions prior to 1.2.4 and demonstrates a classic memory leak pattern that can be exploited remotely to consume system resources and ultimately cause denial of service conditions. The vulnerability specifically targets the software's handling of DNS query parameters, particularly when processing queries with unsupported query types or query classes.
The technical flaw manifests when pdnsd receives DNS queries containing QTYPE or QCLASS values that are not supported by the software's implementation. According to the OUSPG PROTOS DNS test suite documentation, this vulnerability is triggered by sending specially crafted DNS queries that contain invalid or unsupported query parameters. The software fails to properly handle these malformed queries and instead allocates memory for processing them without subsequently releasing that memory, leading to progressive memory consumption over time. This memory leak behavior is particularly dangerous in network services that handle continuous traffic, as it can gradually exhaust available system memory and render the service unusable.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can be leveraged by remote attackers to perform denial of service attacks against systems running vulnerable versions of pdnsd. Network administrators who rely on pdnsd for DNS caching and forwarding services face significant risk since the attack requires no authentication and can be executed from any remote location. The vulnerability's exploitation is straightforward and can be automated, making it an attractive target for malicious actors seeking to disrupt network services. The memory consumption pattern typically progresses slowly but steadily, making it difficult to detect until the system becomes unresponsive or crashes entirely.
Mitigation strategies for this vulnerability involve immediate patching of pdnsd installations to version 1.2.4 or later, where the memory leak has been addressed through proper memory management and input validation. System administrators should also implement network monitoring to detect unusual memory consumption patterns that might indicate exploitation attempts. Additional defensive measures include configuring firewalls to limit DNS query types and implementing rate limiting to prevent abuse of the vulnerable functionality. This vulnerability aligns with CWE-401, which specifically addresses improper release of memory, and represents a clear example of how inadequate input validation can lead to resource exhaustion attacks. The ATT&CK framework categorizes this as a resource exhaustion technique under the 'Denial of Service' tactic, where adversaries consume system resources to prevent legitimate use of services. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious DNS query patterns consistent with this vulnerability's exploitation methods.