CVE-2026-41511: OpenMcdf Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jxpf-xq2m-q525",
  "modified" : "2026-05-13T13:33:51Z",
  "published" : "2026-04-22T22:09:01Z",
  "aliases" : [ "CVE-2026-41511" ],
  "summary" : "OpenMcdf has an Infinite loop DoS via crafted CFB directory cycle",
  "details" : "### Summary\nOpenMcdf 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`.\n\n### Details\nCFB 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.\n\nTwo distinct code paths are affected:\n\n- **`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.\n- **`Storage.OpenStream()`** - `DirectoryTree.TryGetDirectoryEntry` loops indefinitely inside `DirectoryEntries.TryGetSibling` during the name lookup.\n\n### PoC\nA crafted CFB file with a sibling cycle (see attached) triggers the issue with the following code:\n\n```csharp\nusing OpenMcdf;\n\nusing var ms = new MemoryStream(File.ReadAllBytes(\"crafted.cfb\"));\nusing var root = RootStorage.Open(ms);\n\n// Never returns - EnumerateEntries loops indefinitely\nforeach (var entry in root.EnumerateEntries())\n{\n    Console.WriteLine(entry.Name);\n\n    if (entry.Type == EntryType.Stream)\n        root.OpenStream(entry.Name); // also hangs depending on the cycle structure\n}\n```\n\n### Impact\nA denial of service affecting any application that opens untrusted CFB files with OpenMcdf. A small crafted input carrying a valid CFB magic header (`D0 CF 11 E0 A1 B1 1A E1`) is sufficient to pass initial format validation and reach the vulnerable traversal code. No exception is thrown, so `try/catch` cannot protect callers. The affected thread is unrecoverable without killing the process.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "OpenMcdf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/openmcdf/openmcdf/security/advisories/GHSA-jxpf-xq2m-q525"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-41511"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/openmcdf/openmcdf/commit/24f445a557fc4f46461cf6d02d296cce16c293a0"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/openmcdf/openmcdf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/openmcdf/openmcdf/releases/tag/v3.1.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-835" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-22T22:09:01Z",
    "nvd_published_at" : "2026-05-08T19:16:31Z"
  }
}