Microsoft Exchange is impacted by four zero-day vulnerabilities that attackers can exploit remotely to execute arbitrary code or disclose sensitive information on affected installations. The zero-day vulnerabilities were disclosed by Trend Micro's Zero Day Initiative yesterday, who reported them to Microsoft on September 7th and 8th, 2023. Despite Microsoft acknowledging the reports, its security engineers decided the flaws weren't severe enough to guarantee immediate servicing, postponing the fixes for later. ZDI disagreed with this response and decided to publish the flaws under its own tracking IDs to warn Exchange admins about the security risks. ZDI-23-1578 - A remote code execution flaw in the 'ChainedSerializationBinder' class, where user data isn't adequately validated, allowing attackers to deserialize untrusted data. Successful exploitation enables an attacker to execute arbitrary code as 'SYSTEM,' the highest level of privileges on Windows. ZDI-23-1579 - Located in the 'DownloadDataFromUri' method, this flaw is due to insufficient validation of a URI before resource access. Attackers can exploit it to access sensitive information from Exchange servers. ZDI-23-1581 - Present in the CreateAttachmentFromUri method, this flaw resembles the previous bugs with inadequate URI validation, again, risking sensitive data exposure. All these vulnerabilities require authentication for exploitation, which reduces their severity CVSS rating to between 7.1 and 7.5. Requiring authentication is a mitigation factor and possibly why Microsoft did not prioritize the fixing of the bugs. It should be noted that cybercriminals have many ways to obtain Exchange credentials, including brute-forcing weak passwords, performing phishing attacks, purchasing them, or acquiring them from info-stealer logs. ZDI suggests that the only salient mitigation strategy is to restrict interaction with Exchange apps. We also suggest implementing multi-factor authentication to prevent cybercriminals from accessing Exchange instances even when account credentials have been compromised. We appreciate the work of this finder submitting these issues under coordinated vulnerability disclosure, and we're committed to taking the necessary steps to help protect customers. Millions of Exim mail servers exposed to zero-day RCE attacks. 3,000 Apache ActiveMQ servers vulnerable to RCE attacks exposed online. HelloKitty ransomware now exploiting Apache ActiveMQ flaw in attacks. F5 fixes BIG-IP auth bypass allowing remote code execution attacks. Critical RCE flaws found in SolarWinds access audit solution.
This Cyber News was published on www.bleepingcomputer.com. Publication date: Thu, 30 Nov 2023 23:19:27 +0000