CVE-2020-6079 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 decoding of the domain name performed by rr_decode.
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Analysis
by VulDB Data Team • 05/05/2026
The vulnerability identified as CVE-2020-6079 represents a critical denial-of-service flaw within the Videolabs libmicrodns 0.1.0 library implementation. This issue specifically manifests in the resource allocation handling mechanisms when processing multicast domain name system messages, commonly known as mDNS messages. The library's failure to properly manage memory allocation during error conditions creates a persistent resource leak that can accumulate over time and ultimately lead to system instability or complete service unavailability.
The technical root cause of this vulnerability lies in the improper memory management during the decoding process of domain names within mDNS records. When the library encounters malformed or unexpected mDNS messages, the rr_decode function fails to release previously allocated memory resources, resulting in a gradual consumption of available system memory. This memory leak occurs specifically during error handling scenarios where the normal execution flow is interrupted, but cleanup routines are not executed properly. The vulnerability is particularly dangerous because it can be triggered repeatedly through the sending of malformed mDNS messages, allowing an attacker to systematically exhaust system resources without requiring sophisticated exploitation techniques.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of network services that depend on mDNS functionality. Systems utilizing libmicrodns for network discovery, service advertisement, or device communication may become unresponsive or crash entirely when subjected to sustained attacks. This vulnerability affects any application or device that relies on the affected library for mDNS processing, including network infrastructure equipment, IoT devices, and enterprise networking solutions that implement multicast DNS for service discovery. The resource exhaustion can lead to cascading failures across networked systems that depend on continuous mDNS availability for proper operation.
Mitigation strategies for CVE-2020-6079 should focus on immediate library updates to versions that address the memory leak issue, as well as implementing network-level protections against malformed mDNS traffic. Organizations should consider deploying rate limiting mechanisms to restrict the number of mDNS messages processed within specific time intervals, thereby preventing rapid resource exhaustion. Additionally, implementing proper memory monitoring and alerting systems can help detect early signs of resource depletion that may indicate exploitation attempts. Network segmentation and firewall rules can be configured to limit mDNS traffic to trusted network segments, reducing the attack surface for potential exploitation. The vulnerability aligns with CWE-401, which describes improper release of memory, and represents a classic example of how memory management errors can be exploited to create denial-of-service conditions that align with techniques documented in the ATT&CK framework under process injection and resource exhaustion tactics.