# CVE-2026-55373: OpenEXR: OpenEXRUtil SampleCountChannel endEdit() can loop forever on UINT_MAX sample counts

> An attacker can cause an infinite loop and denial of service in OpenEXR by providing a specific sample count value that triggers an integer overflow in size calculation.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** AZL-97623, BELL-CVE-2026-55373, DEBIAN-CVE-2026-55373, ECHO-3c1f-3605-c2d9, GHSA-mff9-68x3-h8rh, MINI-rhff-q6mw-xchj, UBUNTU-CVE-2026-55373

## What is CVE-2026-55373?

CVE-2026-55373 is a medium-severity denial of service vulnerability in AcademySoftwareFoundation openexr, published on 25 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

OpenEXR is the reference implementation and specification for the EXR image format, widely used in the motion picture industry. Versions prior to 3.2.10, 3.3.12, and 3.4.13 contain an infinite-loop vulnerability in SampleCountChannel. The helper roundListSizeUp() rounds a sample-list size up to the next power of two using repeated unsigned left shifts, which terminates for normal values but fails for UINT_MAX: the sequence reaches 0x80000000, and the next left shift wraps the 32-bit value to 0. Because 0 remains less than UINT_MAX, the loop never progresses and never exits. The bug is reachable through public OpenEXRUtil APIs, either by editing the sample-count buffer through SampleCountChannel::Edit (whose destructor calls endEdit()) or by calling SampleCountChannel::set(x, y, UINT_MAX) on a valid pixel. This issue has been fixed in versions 3.2.10, 3.3.12, and 3.4.13.

Weakness: CWE-835 (Loop with Unreachable Exit Condition), CWE-400 (Uncontrolled Resource Consumption), CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-55373?


## How do I fix CVE-2026-55373?

Upgrade to a fixed version.

## Is CVE-2026-55373 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55373 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55373 and fix it if it is affected.

What it is: CVE-2026-55373 is a medium-severity denial of service vulnerability in AcademySoftwareFoundation openexr, published on 25 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55373 exists.

Affected product: AcademySoftwareFoundation 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-2026-55373/ (Markdown: https://insights.sbomify.com/CVE-2026-55373/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55373
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55373
- OSV: https://osv.dev/vulnerability/CVE-2026-55373

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-55373/
Summaries are generated and may contain mistakes; the official description above is the record.