CVE-2026-12912 is a heap-based buffer overflow vulnerability in libtiff affecting Red Hat Enterprise Linux 10. The vulnerability occurs during decoding of PixarLog-compressed TIFF images when the library is explicitly configured to use the PIXARLOGDATAFMT_8BITABGR output format with SamplesPerPixel set to 3. This specific combination leads to a heap overflow due to improper handling of stride values. Exploitation requires processing a specially crafted TIFF image under these conditions. The vulnerability can result in arbitrary code execution or denial of service. Standard image reading functions like TIFFReadRGBAImage are not directly impacted. Red Hat has issued a security advisory (RHSA-2026:34890) and released updated libtiff packages (4.7.1-2.4.hum1) to fix this issue.

The vulnerability allows a local attacker with the ability to process specially crafted PixarLog-compressed TIFF images to cause a heap-based buffer overflow. This can lead to arbitrary code execution, compromising confidentiality, integrity, and availability, or cause a denial of service by crashing the affected application. The CVSS v3.1 score is 7.3 (high severity) with low attack complexity and privileges required, but user interaction is needed. The scope remains unchanged.

Red Hat has released updated libtiff packages (version 4.7.1-2.4.hum1) that fix this vulnerability. Users should apply these updates promptly. Additionally, applications processing untrusted TIFF images should avoid explicitly configuring the PIXARLOGDATAFMT_8BITABGR output format with three samples per pixel when decoding PixarLog-compressed TIFF images, as this specific configuration triggers the vulnerability. Standard image reading functions that do not select this format are not affected.