# CVE-2026-34378: OpenEXR has a signed integer overflow in generic_unpack() when parsing EXR files with crafted negative dataWindow.min.x

> An attacker can cause a denial of service by crafting an EXR file with a negative dataWindow value, triggering an integer overflow in OpenEXR.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** BELL-CVE-2026-34378, DEBIAN-CVE-2026-34378, GHSA-v76p-4qvv-vh4g, JLSEC-2026-142, UBUNTU-CVE-2026-34378

## What is CVE-2026-34378?

CVE-2026-34378 is a medium-severity vulnerability in Openexr Openexr, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. From 3.4.0 to before 3.4.9, a missing bounds check on the dataWindow attribute in EXR file headers allows an attacker to trigger a signed integer overflow in generic_unpack(). By setting dataWindow.min.x to a large negative value, OpenEXRCore computes an enormous image width, which is later used in a signed integer multiplication that overflows, causing the process to terminate with SIGILL via UBSan. This vulnerability is fixed in 3.4.9.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-34378?

It affects 1 product.


Products: Openexr Openexr.

## How do I fix CVE-2026-34378?

Upgrade to a fixed version.

## Is CVE-2026-34378 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34378 exists.

## Other vulnerabilities in Openexr Openexr

- [CVE-2023-5841](https://insights.sbomify.com/CVE-2023-5841/): OpenEXR Heap Overflow in Scanline Deep Data Parsing (critical 9.1)
- [CVE-2026-41142](https://insights.sbomify.com/CVE-2026-41142/): OpenEXR is Vulnerable to Integer overflow in ImageChannel::resize leads to heap OOB write via OpenEXRUtil public API (high 8.8)
- [CVE-2026-42216](https://insights.sbomify.com/CVE-2026-42216/): OpenEXR: Out-of-bounds read in `IDManifest::init()` during prefix expansion (high 8.8)
- [CVE-2017-9111](https://insights.sbomify.com/CVE-2017-9111/): OpenEXR invalid write (high 8.8)
- [CVE-2017-9113](https://insights.sbomify.com/CVE-2017-9113/): Memory corruption in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34378 and fix it if it is affected.

What it is: CVE-2026-34378 is a medium-severity vulnerability in Openexr Openexr, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, 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-2026-34378 exists.

Affected product: Openexr Openexr. 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-2026-34378/ (Markdown: https://insights.sbomify.com/CVE-2026-34378/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34378
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34378
- OSV: https://osv.dev/vulnerability/CVE-2026-34378

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34378/
Summaries are generated and may contain mistakes; the official description above is the record.