OpenMcdf has an Infinite loop DoS via 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-2026-41511: 0.19% estimated exploitation activity in the next 30 days; percentile 8.36 (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 OpenMcdf does not detect cycles in the directory entry red-black tree of a Compound File Binary (CFB) document. A crafted CFB file with a cycle in the LeftSiblingID / RightSiblingID chain causes Storage.EnumerateEntries() and Storage.OpenStream() to loop indefinitely, consuming the calling thread with no possibility of recovery via try/catch. Details CFB directory entries form a red-black tree linked by LeftSiblingID and RightSiblingID fields. OpenMcdf's DirectoryTreeEnumerator and DirectoryTree.TryGetDirectoryEntry traverse this tree without tracking visited node IDs, so a crafted cycle (e.g. entry A's RightSiblingID points to entry B, and entry B's LeftSiblingID points back to entry A) causes traversal to loop indefinitely. Two distinct code paths are affected: - Storage.EnumerateEntries() - DirectoryTreeEnumerator.MoveNext() never returns false; the same entry is yielded on every iteration and the caller's foreach never exits. Heap grows unboundedly as entries accumulate.…

Published by the source

22 Apr 2026, 22:09 UTC

Last modified by the source

13 May 2026, 13:33 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jxpf-xq2m-q525

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-41511

Advisory: OpenMcdf has an Infinite loop DoS via crafted CFB directory cycle
IDs: CVE-2026-41511, GHSA-jxpf-xq2m-q525
Record: https://patchnext.com/advisories/cve-2026-41511 (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 3.1.3. A vendor fix does not mean a deployment is fixed.

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

## 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-jxpf-xq2m-q525 (GitHub-reviewed advisory GHSA-jxpf-xq2m-q525 lists affected ranges: NuGet openmcdf >=0 <3.1.3)

Commands are suggestions: review each one before running it.