CVE-2023-29469: 
NixOS vulnerability analysis and mitigation

An issue was discovered in libxml2 before 2.10.4. When hashing empty dict strings in a crafted XML document, xmlDictComputeFastKey in dict.c can produce non-deterministic values, leading to various logic and memory errors, such as a double free. This behavior occurs because there is an attempt to use the first byte of an empty string, and any value is possible (not solely the '\0' value) (NVD, MITRE CVE).

The vulnerability affects the xmlDictComputeFastKey function in dict.c of libxml2. The issue manifests when processing empty dictionary strings in XML documents, where the function attempts to use the first byte of an empty string, potentially leading to non-deterministic values. The vulnerability has been assigned a CVSS v3.1 Base Score of 6.5 (Medium) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H (NVD, Ubuntu Security).

The vulnerability can result in various logic and memory errors, most notably a double free condition. This can lead to denial of service (DoS) when successfully exploited. The vulnerability affects the availability of the system while having no direct impact on confidentiality or integrity (NetApp Advisory).

The vulnerability has been fixed in libxml2 version 2.10.4. Various distributions have released patched versions: Debian 10 (buster) fixed in version 2.9.4+dfsg1-7+deb10u6, Ubuntu has released fixes for multiple versions including 22.04 LTS (2.9.13+dfsg-1ubuntu0.3) and 20.04 LTS (2.9.10+dfsg-5ubuntu0.20.04.6) (Debian Security, Ubuntu Security).