CVE-2020-6080 in libmicrodns
Summary
by MITRE
An exploitable denial-of-service vulnerability exists in the resource allocation handling of Videolabs libmicrodns 0.1.0. When encountering errors while parsing mDNS messages, some allocated data is not freed, possibly leading to a denial-of-service condition via resource exhaustion. An attacker can send one mDNS message repeatedly to trigger this vulnerability through the function rr_read_RR [5] reads the current resource record, except for the RDATA section. This is read by the loop at in rr_read. For each RR type, a different function is called. When the RR type is 0x10, the function rr_read_TXT is called at [6].
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Analysis
by VulDB Data Team • 01/29/2025
The vulnerability described in CVE-2020-6080 represents a critical resource management flaw within the Videolabs libmicrodns 0.1.0 library that operates as a lightweight implementation of the Multicast DNS protocol. This library is commonly used in network discovery and service advertisement applications, making it a potential target for attackers seeking to disrupt network services. The issue manifests specifically during the parsing of malformed or error-inducing mDNS messages, where the library fails to properly release allocated memory resources when encountering parsing errors, creating a predictable pattern of resource leakage that can be exploited systematically.
The technical root cause of this vulnerability lies in the improper memory deallocation mechanism within the mDNS message parsing functions, particularly when processing resource records of type 0x10 which corresponds to TXT records. The parsing logic in rr_read_RR function correctly handles the basic resource record structure but fails to account for error conditions that occur during the RDATA section processing. When the rr_read_TXT function is invoked to handle TXT record data, it processes the record content without proper cleanup of previously allocated memory in error scenarios. This memory leak occurs because the library's error handling path does not execute the necessary deallocation routines, causing allocated memory chunks to remain in use indefinitely.
The operational impact of this vulnerability creates a straightforward denial-of-service condition that can be triggered by sending repeated malformed mDNS messages to a target system. The attacker needs only to craft a specific mDNS message with a TXT record and send it repeatedly to cause progressive memory exhaustion, eventually leading to system instability or complete service unavailability. This vulnerability is particularly dangerous because it requires minimal resources to execute and can be automated, making it an attractive attack vector for network disruption campaigns. The memory leak accumulates over time with each processed message, making the impact more severe as the attack continues.
This vulnerability maps directly to CWE-401, which describes improper release of memory before removing the last reference, and aligns with ATT&CK technique T1499.004 for network denial-of-service attacks. The attack pattern follows a typical resource exhaustion methodology where the attacker leverages a library's memory management flaw to consume system resources progressively. The affected library's use in various network applications means that exploitation could impact multiple systems simultaneously, potentially affecting entire network segments. Organizations relying on libmicrodns for network discovery services should consider this vulnerability as a high-priority security concern that could lead to service degradation or complete network disruption.
Mitigation strategies should focus on immediate library updates to versions that address the memory leak issue, as well as implementing network-level protections such as rate limiting for mDNS traffic and monitoring for unusual patterns of resource record processing. System administrators should also consider deploying intrusion detection systems that can identify and block malformed mDNS traffic patterns that could indicate exploitation attempts. Additionally, regular memory usage monitoring and automated alerting systems can help detect the early signs of resource exhaustion before it leads to complete service disruption, providing an additional layer of defense against this specific vulnerability pattern.