{"id":"GHSA-jxpf-xq2m-q525","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.","aliases":["CVE-2026-41511"],"modified":"2026-05-13T13:52:34.912355Z","published":"2026-04-22T22:09:01Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-04-22T22:09:01Z","nvd_published_at":"2026-05-08T19:16:31Z","cwe_ids":["CWE-835"],"severity":"MODERATE"},"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"}],"affected":[{"package":{"name":"OpenMcdf","ecosystem":"NuGet","purl":"pkg:nuget/OpenMcdf"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.3"}]}],"versions":["1.5.4","1.5.4.1","1.5.4.22637","2.0.5739","2.0.5739.40493","2.1.0.33051","2.1.2.1274","2.1.3.34720","2.1.3.34730","2.1.4.23498","2.1.5.22659","2.1.6.28924","2.2.0.1","2.2.1.12","2.2.1.2","2.2.1.3","2.2.1.4","2.2.1.5","2.2.1.6","2.2.1.8","2.2.1.9","2.3.0","2.3.1","2.4.0","2.4.1","3.0.0","3.0.0-preview1","3.0.1","3.0.2","3.0.3","3.1.0","3.1.1","3.1.2"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-jxpf-xq2m-q525/GHSA-jxpf-xq2m-q525.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}