OpenSlide is a C library used to read whole slide image files. A change in libtiff 4.7.1 causes the openslide_read_region() routine to request a full‑height destination for a partial bottom tile row in certain TIFF formats, allowing uninitialized heap memory to be returned as pixel data. The memory content that leaks depends on pixel transparency handling and recompression; if an attacker supplies a crafted but valid slide, the uninitialized data can be extracted.

The vulnerability affects OpenSlide library builds prior to version 4.0.1. Specifically, the official binary builds 4.0.0.10 and 4.0.0.11, which bundle libtiff 4.7.1, are impacted. OpenSlide 4.0.0.12 and later, as well as any builds that use libtiff versions earlier than 4.7.1, are not affected.

The CVSS score of 5.3 places this as a medium severity issue, but the EPSS score of <1% indicates a very low probability of exploitation at present. The vulnerability is not listed in the CISA KEV catalog. Exploitation requires an attacker to supply a specially crafted slide to a service that renders slides via OpenSlide; thus the likely attack vector is a network service that accepts external slide data. If successful, the exposed uninitialized memory could leak sensitive information from the host process.