This vulnerability involves an out-of-bounds read in the function fz_subset_cff_for_gids of the subset-cff.c file in Artifex MuPDF versions up to 1.28.0. The flaw exists in the CFF Index Handler component and can be triggered by local attackers without user interaction. The vulnerability could potentially lead to information disclosure or application instability due to reading memory outside intended bounds. The vendor has not issued a patch or official remediation at this time.

The impact is limited to local attackers who can execute the out-of-bounds read, potentially leading to information disclosure or application crashes. There is no indication of remote exploitation, privilege escalation, or user interaction required. No known exploits have been observed in the wild, and the severity is rated medium with a CVSS score of 4.8.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since the vendor has not responded or provided a fix, users should monitor official channels for updates. Until a patch is available, restrict local access to systems running affected versions of MuPDF and consider using alternative PDF rendering tools if local threat risk is high.