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CVE-2026-45785 medium CVSS 6.2

Vulnerability in OpenMcdf (CVE-2026-45785)

Summary

Vulnerability in OpenMcdf (CVE-2026-45785). Risk of unauthorized operations or information disclosure. Exploitable via DirectoryTree.TryGetDirectoryEntry. Mitigation: upgrade to 3.1.4 or later.

Original description

The description as published by the source.

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 iterate EnumerateEntries() and call OpenStream(entry.Name) per Stream entry. With Brent's algorithm catching the enumeration cycle but not the per-entry lookup, callers can still hang as soon as they touch a streamed entry.

PoC

Two minimal repros attached, demonstrating the same lookup-loop bug reached via two different public APIs:

  • repro_lookup.cfb (5,632 by…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-45785 has been found in OpenMcdf.
Attackers can target a specific entry point like DirectoryTree.TryGetDirectoryEntry over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.2/10.
What to do: upgrade OpenMcdf to 3.1.4 or later.
If unsure, ask your IT team or search "OpenMcdf CVE-2026-45785" on the vendor's site.

CVE-2026-45785 (OpenMcdf) — CWE-835 / CVSS v3 6.2
Attack vector: local / unauthenticated / no user interaction
Attack surface: DirectoryTree.TryGetDirectoryEntry / TryGetSibling / TryGetDirectoryEntry / DirectoryTreeEnumerator
Patched: 3.1.4 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-835) exists in OpenMcdf. Attackers reach the vulnerable code path via DirectoryTree.TryGetDirectoryEntry without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of OpenMcdf. Attack surface: DirectoryTree.TryGetDirectoryEntry / TryGetSibling / TryGetDirectoryEntry / DirectoryTreeEnumerator.

🔥 Severity

Severity: Medium (CVSS 6.2/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 3.1.4.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'OpenMcdf' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'OpenMcdf' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で OpenMcdf を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade OpenMcdf to 3.1.4

    ステージング環境で 3.1.4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

nuget OpenMcdf
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.4"}]}]

References

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