Description

Server-side request forgery (ssrf) in Microsoft Exchange Online allows an unauthorized attacker to elevate privileges over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "10.0",
  "pubDate": "2026-08-20T22:17:54.897Z",
  "pubdate": "2026-08-20T22:17:54.897Z",
  "executiveSummary": "A Server-Side Request Forgery (SSRF) vulnerability has been identified within Microsoft Exchange Online. This security flaw enables an unauthorized remote attacker to manipulate server-side HTTP requests, leading to privilege escalation over a network.\nThe affected product is Microsoft Exchange Online, a cloud-based messaging and collaboration platform. The risk implications are severe, as successful exploitation bypasses standard authorization boundaries and grants unauthorized elevated privileges within the targeted environment.\nThe attacker capabilities include initiating arbitrary outbound requests originating from the context of the vulnerable Exchange Online server infrastructure. Exploitation requires network access to the target service and the ability to induce the server into processing maliciously crafted Uniform Resource Identifiers or network routing parameters.\nNo specific authentication prerequisites are mandated for initiating the attack vectors, classifying the threat as an unauthorized network-based privilege escalation vector.",
  "technicalDetails": "The root cause of the vulnerability stems from insufficient validation and sanitization of user-supplied input utilized within server-side request generation functions inside Microsoft Exchange Online.\nWhen a user or automated component submits input that is subsequently parsed to construct outgoing network requests, the lack of strict allowlisting or proper URL schema parsing permits attackers to redirect internal routing logic.\nThe exploitation method relies on supplying crafted payloads via vulnerable input parameters, forcing the Microsoft Exchange Online server to dispatch requests to internal resources, metadata endpoints, or restricted external services that are normally inaccessible to unprivileged network entities.\nThe attack flow proceeds as follows: First, the unauthorized attacker identifies an exposed entry point within Microsoft Exchange Online that handles remote resource fetching or proxy functionalities. Second, the attacker crafts a malicious request payload containing targeted internal IP addresses, loopback addresses, or alternative protocol schemes.\nThird, the vulnerable component processes the input without adequate validation and executes the outbound connection on behalf of the attacker. Fourth, the server receives the response from the internal resource and inadvertently leaks sensitive data or executes privileged operational commands depending on how the internal service handles the proxied request.\nThe vulnerable component resides within the request handling and proxy routing modules of Microsoft Exchange Online. The network exposure is remote, operating over standard network protocols utilized by the service.\nAuthentication requirements are minimal to none for the initial request trigger, and privilege requirements for the attacker are unauthorized prior to exploitation.\nThe post-exploitation impact encompasses unauthorized privilege escalation, potential exposure of internal infrastructure data, lateral movement capabilities within the cloud architecture, and manipulation of backend services accessible only via the trusted server-side context."
}