Debian 11: DLA-4251-1 libxml2 Important Denial of Service Risk

CVE-2024-34459

Zhineng Zhong discovered that formatting error messages with `xmllint
--htmlout` could result in a buffer over-read.

CVE-2025-6021

Ahmed Lekssays discovered an integer overflow issue in
`xmlBuildQName()` which could result in memory corruption or a
denial of service when processing crafted input.

CVE-2025-6170

Ahmed Lekssays discovered a stack-based buffer overflow issue in the
command-parsing logic of the interactive shell in xmllint.

CVE-2025-49794

Nikita Sveshnikov discovered a heap use-after-free issue in the
schematron. When processing XPath expressions in Schematron schema
elements ``, a pointer to freed memory is
returned and then accessed, leading to undefined behavior or
potential crashes.

CVE-2025-49796

Nikita Sveshnikov discovered a type confusion issue in the
schematron. Processing `sch:name` elements and accessing namespace
information may lead to leading to memory corruption or undefined
behavior.