Security Digest · Vulnerability record
CVE-2026-84383: libheif: Heap buffer overflow in `scale_nearest_neighbor()` via duplicate Alpha planes from nested `iden`/`auxl` items
libheif is a HEIF and AVIF file format decoder and encoder.
CVSS 9.8 Critical EPSS 0.6% · p48 Patch this week
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- 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.
Weakness type: CWE-787.
Product: strukturag libheif · Assigned by: GitHub_M · Published: 2026-09-18
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| strukturag | libheif | >= 1.22.0, < 1.23.2 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- 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.
Timeline
- — erroneo.us brief: Next.js: Windows, AVIF and next/og RCEs (Aug-Sep 2026)
- — CVE record last updated
- — CVE record published by GitHub_M
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- CVE.org record CVE-2026-84383 cve.org
- NVD entry CVE-2026-84383 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com