What’s Vulnerable › Vulnerabilities

CVE-2026-45785: OpenMcdf: Uncatchable infinite loop in DirectoryTree.TryGetDirectoryEntry on crafted CFB directory cycle

• Severity: medium (CVSS 6.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-17 · updated 2026-07-23
• Weakness: CWE-835

Description

OpenMcdf is a fully .NET / C# library to manipulate Compound File Binary File Format files, also known as Structured Storage. In 3.1.3 and earlier, 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, and the bug is reachable from RootStorage.OpenStorage(name), TryOpenStorage(name), OpenStream(name), and TryOpenStream(name), causing an unrecoverable denial of service. This issue is fixed in version 3.1.4.

Affected products

• openmcdf: before 3.1.4

References

• https://github.com/openmcdf/openmcdf/commit/c6f82db722bd85db7b0caed3ca1aa374f1e07bc7
• https://github.com/openmcdf/openmcdf/releases/tag/v3.1.4
• https://github.com/openmcdf/openmcdf/security/advisories/GHSA-5qwm-7pvp-w988
• https://github.com/openmcdf/openmcdf/security/advisories/GHSA-5qwm-7pvp-w988

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