# CVE-2026-45785: OpenMcdf: Uncatchable infinite loop in DirectoryTree.TryGetDirectoryEntry on crafted CFB directory cycle

> Attackers can cause an infinite loop and denial of service in OpenMcdf by providing a crafted Compound File Binary file with cyclic directory entries.

- **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:** 17 Jul 2026
- **Updated:** 21 Jul 2026
- **Also known as:** GHSA-5qwm-7pvp-w988

## What is CVE-2026-45785?

CVE-2026-45785 is a medium-severity denial of service vulnerability in openmcdf, published on 17 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

OpenMcdf is a fully .NET / C# library to manipulate Compound File Binary File Format files, also known as Structured Storage. In 3.1.3 and earlier, the BST name-lookup loop in DirectoryTree.TryGetDirectoryEntry (OpenMcdf/DirectoryTree.cs:35-46) walks directory entries by repeatedly calling directories.TryGetSibling(child, siblingType, validateColor). A crafted CFB file with cyclic Left/Right sibling links among directory entries, constructed so the per-step BST-order check in TryGetSibling (DirectoryEntries.cs:84-85) is satisfied at every step, drives this while (child is not null) loop forever. There is no cycle detection in TryGetDirectoryEntry, and the bug is reachable from RootStorage.OpenStorage(name), TryOpenStorage(name), OpenStream(name), and TryOpenStream(name), causing an unrecoverable denial of service. This issue is fixed in version 3.1.4.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2026-45785?

2 open source packages ship an affected version, including OpenMcdf.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `OpenMcdf` | NuGet | All versions | 3.1.4 |
| `OpenMcdf` | NuGet | All versions | 3.1.4 |

## How do I fix CVE-2026-45785?

Upgrade OpenMcdf to 3.1.4 or later.

## Is CVE-2026-45785 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45785 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45785 and fix it if it is affected.

What it is: CVE-2026-45785 is a medium-severity denial of service vulnerability in openmcdf, published on 17 Jul 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-2026-45785 exists.

Affected packages and fixed versions:
- OpenMcdf (NuGet): affected all versions; fixed in 3.1.4
- OpenMcdf (NuGet): affected all versions; fixed in 3.1.4

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-2026-45785/ (Markdown: https://insights.sbomify.com/CVE-2026-45785/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45785
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45785
- OSV: https://osv.dev/vulnerability/CVE-2026-45785

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45785/
Summaries are generated and may contain mistakes; the official description above is the record.