CVE-2026-47631: Microsoft Exchange Server Spoofing Vulnerability

Synopsis

Cross-site scripting (XSS) in Microsoft Exchange Server allows an unauthenticated network attacker to perform spoofing attacks against users who interact with a malicious link or crafted web content served by the Exchange web interface. The vulnerability stems from improper neutralization of user-supplied input during web page generation, meaning attacker-controlled content is rendered in the victim's browser without adequate sanitization. Successful exploitation lets an attacker impersonate trusted content or users, which can lead to credential theft, session hijacking, or unauthorized actions taken on behalf of the victim. Patched-image rebuilds at the fix versions are available on HarborGuard for environments running an affected Exchange Server version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the Exchange Server's web interface over the network; AV:N means no local or physical access is required.

• AuthenticationNot required

  No account or credentials are needed to deliver the malicious payload; PR:N confirms the attacker is entirely unauthenticated.

• Victim interactionRequired

  A legitimate user must take an action such as clicking a crafted link or visiting a malicious page that triggers the injected script; UI:R reflects this social-engineering dependency.

• Attack complexityDetail

  Attack complexity is low (AC:L), meaning the exploit is reliable and does not depend on race conditions, specific memory layouts, or other hard-to-control environmental factors.

Blast Radius

• Reads session tokens or authentication cookies from the victim's browser, enabling account takeover without knowing the victim's password.
• Injects script that performs actions inside Exchange on behalf of the victim, such as forwarding emails or modifying mailbox rules.
• Renders attacker-controlled content in the Exchange web interface, allowing convincing phishing pages served from a trusted domain.