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

> A heap-buffer-overread in OpenImageIO allows attackers to disclose adjacent heap memory or cause a crash via crafted IFF images.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 18 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-59956, GHSA-hjfv-gvxc-qgvh, UBUNTU-CVE-2026-59956

## What is CVE-2026-59956?

CVE-2026-59956 is a medium-severity memory corruption vulnerability in Openimageio Openimageio, published on 18 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-59956?

It affects 1 product.


Products: Openimageio Openimageio.

## How do I fix CVE-2026-59956?

Upgrade to a fixed version.

## Is CVE-2026-59956 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59956 exists.

## Other vulnerabilities in Openimageio Openimageio

- [CVE-2024-55192](https://insights.sbomify.com/CVE-2024-55192/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-55194](https://insights.sbomify.com/CVE-2024-55194/): Memory corruption in n/a (critical 9.8)
- [CVE-2023-42299](https://insights.sbomify.com/CVE-2023-42299/): Memory corruption in n/a (critical 9.8)
- [CVE-2022-38143](https://insights.sbomify.com/CVE-2022-38143/): Memory corruption in OpenImageIO (critical 9.8)
- [CVE-2026-43908](https://insights.sbomify.com/CVE-2026-43908/): OpenImageIO: Signed integer overflow in ConvertCbYCrYToRGB leads to heap out-of-bounds write in DPX 4:2:2 decoder (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59956 and fix it if it is affected.

What it is: CVE-2026-59956 is a medium-severity memory corruption vulnerability in Openimageio Openimageio, published on 18 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59956 exists.

Affected product: Openimageio Openimageio. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-59956/ (Markdown: https://insights.sbomify.com/CVE-2026-59956/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59956
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59956
- OSV: https://osv.dev/vulnerability/CVE-2026-59956

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-59956/
Summaries are generated and may contain mistakes; the official description above is the record.