CVE-2026-84450 libheif: `clap` + oversized `ispe` aborts on an assert in `Fraction::Fraction` (incomplete fix for CVE-2026-62289)
A crafted HEIF/AVIF image can cause an application using libheif to abort due to an assertion failure during crop calculations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-84450?
CVE-2026-84450 is a medium-severity denial of service vulnerability in strukturag libheif, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
libheif is a HEIF and AVIF file format decoder and encoder. From 1.19.0 until 1.23.3, a crafted image item containing a clap property and an ispe width or height greater than INT32_MAX + 1 can reach crop calculations through heif_image_handle_get_image_tiling(). Box_clap::left_rounded() or Box_clap::top_rounded() passes the image dimension minus one to Fraction::Fraction(), whose uint32_t constructor uses an assertion as input validation, causing assert-enabled builds to abort. Release builds can instead compute invalid crop geometry, and the tiling API returns dimensions that the normal decode security limits reject. This issue is fixed in version 1.23.3.
Weakness: CWE-617
Which versions are affected by CVE-2026-84450?
How do I fix CVE-2026-84450?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-84450 being exploited?
There is no known exploitation of CVE-2026-84450 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-84450, DEBIAN-CVE-2026-84450, ECHO-2ec0-a051-6be2, GHSA-gh5q-69gg-c964, MINI-g6g2-975r-673h.