Description

Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to deny service over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-08-11T17:18:45.197Z",
  "pubdate": "2026-08-11T17:18:45.197Z",
  "executiveSummary": "This vulnerability involves a deserialization of untrusted data flaw affecting Microsoft Exchange Server. The security defect allows an authenticated attacker to compromise system availability over a network connection, resulting in a Denial of Service (DoS) condition.\nFrom a risk perspective, successful exploitation severely impacts the operational availability of enterprise messaging infrastructure. The attack vector requires the adversary to possess specific network access to the target Exchange Server instance and valid authorization to interact with the vulnerable service.\nThe inherent risk of insecure deserialization in enterprise communication servers lies in the potential for memory corruption, resource exhaustion, or application crashes when malicious payloads are processed without adequate validation. Because Microsoft Exchange Server typically operates within core network perimeters with high availability requirements, an unhandled exception or resource exhaustion triggered by maliciously crafted serialized objects directly undermines business continuity.\nMitigation requires careful application of vendor-supplied patches, adherence to the principle of least privilege regarding user access controls, and network segmentation to restrict unauthorized entities from reaching sensitive administrative and client-access endpoints.",
  "technicalDetails": "The root cause of the vulnerability stems from insecure deserialization within Microsoft Exchange Server. The application processes serialized data streams received from network sources without implementing sufficient cryptographic integrity checks, type handling restrictions, or robust validation mechanisms prior to instantiation.\nThe vulnerable component is responsible for handling incoming remote procedure calls or serialized object graphs within the Exchange architecture. When an authorized attacker transmits a specifically crafted payload containing malicious serialized data over the network, the affected parsing routine instantiates the embedded objects within the application memory space.\nThe attack flow proceeds as follows: First, the authenticated adversary establishes a network connection to the targeted Microsoft Exchange Server interface that accepts serialized input. Second, the attacker transmits the malicious payload designed to exploit the deserialization mechanism. Third, the application deserializes the input, triggering unintended code execution paths, excessive memory consumption, or severe exception handling faults that cause the affected service to crash or become unresponsive.\nExploitation requirements dictate that the attacker must possess valid network connectivity and authorization credentials to interact with the vulnerable service endpoints. Privilege requirements involve authenticated access, although the exact privilege level depends on the specific exposed interface utilized for the attack. The post-exploitation impact is strictly confined to a Denial of Service, impairing core messaging services and interrupting client connectivity across the enterprise environment."
}