This vulnerability exists in libxls 1.6.3 and earlier versions within the xls_getCSS() function. It is caused by inadequate validation of a font index controlled by the input file, resulting in a heap-buffer-overflow and use-after-free condition. These memory corruption issues could potentially be exploited if an attacker supplies a crafted XLS file to a system using the vulnerable library.

The vulnerability could allow an attacker to cause memory corruption, potentially leading to application crashes or arbitrary code execution depending on the context in which libxls is used. However, no known exploits in the wild have been reported as of the publication date.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Users should monitor for official fixes or updates from the libxls maintainers and apply them once available. Until then, avoid processing untrusted XLS files with vulnerable versions of libxls.