The xlnt-community library contains a heap‑based buffer overflow in the binary_writer::append function, part of its Compound Document Parser. When processing a specially crafted compound document file, the function writes beyond the bounds of a heap buffer, potentially corrupting adjacent memory and causing application crashes or other memory corruption. The flaw requires local execution, meaning that an attacker must be able to run code in the same context that loads the document. While the CVE description does not explicitly state arbitrary code execution, the availability of a publicly released exploit suggests that attackers could potentially use the overflow to perform local attacks. The weakness maps to CWEs 119 and 122.

The vulnerability affects all versions of the xlnt library up to and including 1.6.1 distributed by xlnt‑community. Any application that incorporates these versions and processes compound document files is susceptible. No other products or library versions are documented as vulnerable.

The CVSS score of 4.8 indicates moderate risk, and the EPSS score of less than 1% shows a low likelihood of exploitation in practice. The flaw requires local execution; an attacker must have code running in the same context that loads a compound document, or the user must be coerced into opening a malicious file. Although no widely confirmed exploitation has been reported, publicly available proof‑of‑concept code exists, underscoring the importance of applying the fix promptly.