Vulnerability in OpenMcdf (CVE-2026-41511)
Summary
Vulnerability in OpenMcdf (CVE-2026-41511). Risk of unauthorized operations or information disclosure. Exploitable via LeftSiblingID. Mitigation: upgrade to 3.1.3 or later.
Original description
The description as published by the source.
OpenMcdf is a fully .NET / C# library to manipulate Compound File Binary File Format files, also known as Structured Storage. Prior to version 3.1.3, 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. This issue has been patched in version 3.1.3.
Source: NIST National Vulnerability Database 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-2026-41511 has been found in OpenMcdf.
Attackers can target a specific entry point like LeftSiblingID 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 3.1.3 or later.
If unsure, ask your IT team or search "OpenMcdf CVE-2026-41511" on the vendor's site.
CVE-2026-41511 (OpenMcdf) — CWE-835 / CVSS v3 6.2
Attack vector: local / unauthenticated / no user interaction
Attack surface: LeftSiblingID / RightSiblingID / DirectoryTreeEnumerator / DirectoryTree.TryGetDirectoryEntry
Patched: 3.1.3 — 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.
A vulnerability (CWE-835) exists in OpenMcdf. Attackers reach the vulnerable code path via LeftSiblingID without authentication.
Check the vendor advisory for the affected versions of OpenMcdf. Attack surface: LeftSiblingID / RightSiblingID / DirectoryTreeEnumerator / DirectoryTree.TryGetDirectoryEntry.
Severity: Medium (CVSS 6.2/10). Risk of unauthorized operations or information disclosure.
Update to 3.1.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
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
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1Identify 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。 -
2Apply patch patch
Upgrade OpenMcdf to 3.1.3ステージング環境で 3.1.3 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。
-
3Post-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
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- web github.com
- web github.com