libheif is a HEIF and AVIF file format decoder and encoder. The fix for CVE-2026-3949 (commit "b97c8b5", PR #1712) introduced an integer overflow in the very security check it added. The check itself can be bypassed, allowing a crafted HEIF file with a VVC track to trigger the same out-of-bounds heap read that CVE-2026-3949 was meant to prevent. This is a separate, currently-unpatched vulnerability. Issue #1712 was closed as fixed without testing the edge case where "size" is near "UINT32_MAX". Version 1.22.0 patches the issue.