CVE-2020-12460: 
NixOS vulnerability analysis and mitigation

OpenDMARC through 1.3.2 and 1.4.x through 1.4.0-Beta1 contains a vulnerability related to improper null termination in the function opendmarc_xml_parse. The vulnerability was discovered in 2020 and affects the OpenDMARC implementation of the DMARC specification, which is used for Domain-based Message Authentication, Reporting & Conformance (CVE Details, Ubuntu Security).

The vulnerability stems from improper null termination in the opendmarc_xml_parse function. When parsing a specially crafted DMARC aggregate report, this can result in a one-byte heap overflow in opendmarc_xml. The issue occurs when a '\0' byte overwrites the heap metadata of the next chunk and its PREV_INUSE flag. The vulnerability has a CVSS 3.1 Base Score of 9.8 (Critical), indicating high severity across confidentiality, integrity, and availability impacts (Ubuntu Security, GitHub Issue).

The vulnerability can cause remote memory corruption when a null byte overwrites the heap metadata of the next chunk and its PREV_INUSE flag. This can lead to a crash during memory deallocation operations and, depending on how the OpenDMARC library is used in linked applications, could potentially allow for arbitrary code execution with the privileges of the process (Gentoo Security, GitHub Issue).

The vulnerability can be triggered remotely by sending a specially crafted DMARC aggregate report to a system running the affected versions of OpenDMARC. The exploitation requires no user interaction or special privileges, making it particularly dangerous for systems processing DMARC reports (Ubuntu Security, Gentoo Security).

The vulnerability has been fixed in OpenDMARC version 1.3.3 and later releases. Users are advised to upgrade to the latest version of OpenDMARC. Various Linux distributions have also released security updates to address this vulnerability, including Ubuntu, Fedora, and Gentoo (Debian LTS, Fedora Update, Gentoo Security).