libheif CVE-2026-41071

The victim must actively open a crafted HEIF sequence file (CVSS UI:A), making passive or zero-click exploitation impossible without an additional delivery vector. The vulnerable code path is specific to HEIF sequence files containing a saiz (sample auxiliary information size) box - standard still-image HEIF files without this box are not affected. No authentication, special privileges, or non-default configuration is required on the target system (CVSS PR:N, AC:L). Exploitation is limited by the requirement for user interaction, the low-to-moderate memory impact (partial heap read, no confirmed write primitive), and the absence of publicly known exploit code. Defenders in environments where HEIF sequence files are not a business requirement can effectively eliminate this attack surface by blocking the file type at ingestion points.

The CVSS 4.0 score of 5.1 (Medium) is consistent with the impact profile: AV:N establishes network reachability through file delivery, AC:L and AT:N confirm no special conditions or prior foothold are needed, PR:N indicates no authentication is required, but UI:A (user must actively open the file) limits opportunistic exploitation. Confidentiality and availability impacts are both rated Low (VC:L, VA:L) with no integrity impact, meaning the realistic worst-case is a partial heap-memory leak or application crash rather than full code execution as currently scored. EPSS of 0.04% at the 11th percentile strongly suggests no observed exploitation activity and low threat-actor interest at this time. No CISA KEV listing and no public exploit code are confirmed. The SUSE tag indicates downstream distribution packaging exposure, which broadens the installed base but does not change the individual risk calculus. One area to monitor: CWE-125 out-of-bounds reads in media parsers have historically been chained as information leaks to defeat ASLR in more complex exploit chains; the current score may understate long-term risk if combined with a write primitive elsewhere in the parser.

An attacker crafts a HEIF sequence file in which the saiz box reports a sample count substantially higher than the number of samples referenced in the track's chunk offset table, then distributes this file via email attachment, web download, or shared storage. When a user on an unpatched system opens the file in any libheif-linked application - an image viewer, a photo editor, or a browser with HEIF support - heif_context_read_from_file() instantiates SampleAuxInfoReader, the loop runs past the end of the chunks heap buffer, and the process either leaks adjacent heap contents (potentially exposing pointers or sensitive data) or crashes with a segmentation fault.