---
title: "CVE-2026-84383: libheif: Heap buffer overflow in `scale_nearest_neighbor()` via duplicate Alpha planes from nested `iden`/`auxl` items"
url: https://erroneo.us/security/cve/CVE-2026-84383/
description: "CVE-2026-84383 (strukturag libheif): libheif is a HEIF and AVIF file format decoder and encoder. From 1.22.0 until 1.23.2, a crafted HEIF, HEIC, or AVIF…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-18
date_modified: 2026-09-30
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-84383"
kev: false
cvss: 9.8
epss: 0.00608
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-84383: libheif: Heap buffer overflow in `scale_nearest_neighbor()` via duplicate Alpha planes from nested `iden`/`auxl` items

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6% , percentile 48: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 48% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Patch this week. Next.js: Windows, AVIF and next/og RCEs (Aug-Sep 2026) — Self-hosted Next.js apps still below 15.5.24 or 16.3.3 should upgrade now, ideally straight to the October releases; Windows hosts and apps optimizing untrusted AVIF images are the urgent cases.

## What it is

libheif is a HEIF and AVIF file format decoder and encoder. From 1.22.0 until 1.23.2, a crafted HEIF, HEIC, or AVIF item graph using nested iden and auxl references can make HeifPixelImage::transferchannelfromimageas() append duplicate Alpha planes with different bit depths to mstorage. HeifPixelImage::scalenearestneighbor() in libheif/image/pixelimage.cc allocates the destination Alpha plane using the first plane's 8-bit depth, then iterates a later 10-bit or 12-bit Alpha component and writes uint16t samples into the same 8-bit allocation. The output geometry controls the overflow extent and the encoded sample values control the data written, allowing a remote file processed by heifdecodeimage() to cause a heap out-of-bounds write. This issue is fixed in version 1.23.2.

## Affected products (CVE record)

- strukturag libheif: >= 1.22.0, < 1.23.2

## Severity

- GitHub_M CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.61% probability of exploitation activity in the next 30 days; percentile 48.

## Sources

- [CVE.org record CVE-2026-84383](https://www.cve.org/CVERecord?id=CVE-2026-84383)
- [NVD entry CVE-2026-84383](https://nvd.nist.gov/vuln/detail/CVE-2026-84383)
- [github.com](https://github.com/strukturag/libheif/security/advisories/GHSA-g89c-p67h-r497)
- [github.com](https://github.com/strukturag/libheif/commit/f4fb8bde4704ebb46e46ff9fb94407c9774153b2)
- [github.com](https://github.com/strukturag/libheif/releases/tag/v1.23.2)

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Source page: https://erroneo.us/security/cve/CVE-2026-84383/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt