OpenMcdf: Uncatchable infinite loop in DirectoryTree.TryGetDirectoryEntry on crafted CFB directory cycle

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.2 · CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-45785: 0.18% estimated exploitation activity in the next 30 days; percentile 8.01 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. Details The recent Brent's-algorithm commit (24f445a) protects DirectoryTreeEnumerator and works correctly for both attached repros - pure EnumerateEntries() throws FileFormatException: Directory tree contains a loop cleanly. The unprotected code path is the lookup-by-name loop, which is reached from multiple public APIs: - RootStorage.OpenStorage(name) / TryOpenStorage(name) - RootStorage.OpenStream(name) / TryOpenStream(name) The second one matters most: typical consumers…

Published by the source

19 May 2026, 19:50 UTC

Last modified by the source

19 May 2026, 19:51 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5qwm-7pvp-w988

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# Patch Next advisory brief: CVE-2026-45785

Advisory: OpenMcdf: Uncatchable infinite loop in DirectoryTree.TryGetDirectoryEntry on crafted CFB directory cycle
IDs: CVE-2026-45785, GHSA-5qwm-7pvp-w988
Record: https://patchnext.com/advisories/cve-2026-45785 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: openmcdf 3.1.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet openmcdf: affected <= 3.1.3; fixed in 3.1.4

## Suggested inspection (read-only)
- NuGet openmcdf: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on openmcdf.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5qwm-7pvp-w988 (GitHub-reviewed advisory GHSA-5qwm-7pvp-w988 lists affected ranges: NuGet openmcdf >=0 <=3.1.3)

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