Microsoft released its monthly security update Tuesday, disclosing more than 120 vulnerabilities across its line of products and software, the most in a single Patch Tuesday in four months.

This batch of updates also includes a fix for a new vulnerability in the Microsoft Windows Support Diagnostic Tool (MSDT) that’s actively being exploited in the wild, according to Microsoft. MSDT was already the target of the so-called “Follina” zero-day vulnerability in June.

In all, August’s Patch Tuesday includes 15 critical vulnerabilities and a single low- and moderate-severity issue. The remainder is classified as “important.”

Two of the important vulnerabilities CVE-2022-35743 and CVE-2022-34713 are remote code execution vulnerabilities in MSDT. However, only CVE-2022-34713 has been exploited in the wild and Microsoft considers it “more likely” to be exploited. Microsoft Exchange Server contains two critical elevation of privilege vulnerabilities, CVE-2022-21980 and CVE-2022-24477. An attacker could exploit this vulnerability by tricking a target into visiting a malicious, attacker-hosted server or website. In addition to applying the patch released today, potentially affected users should enable Extended Protection on vulnerable versions of the server.

The Windows Point-to-Point Tunneling Protocol is also vulnerable to three critical vulnerabilities. Two of them, CVE-2022-35744 and CVE-2022-30133, could allow an attacker to execute remote code on an RAS server machine. The other, CVE-2022-35747, could lead to a denial-of-service condition. CVE-2022-35744 has a CVSS severity score of 9.8 out of 10, one of the highest-rated vulnerabilities this month. An attacker could exploit these vulnerabilities by communicating via Port 1723. Affected users can render these issues unexploitable by blocking that port, though it runs the risk of disrupting other legitimate communications.

Another critical code execution vulnerability, CVE-2022-35804, affects the SMB Client and Server and the way the protocol handles specific requests. An attacker could exploit this on the SMB Client by configuring a malicious SMBv3 server and tricking a user into connecting to it through a phishing link. It could also be exploited in the Server by sending specially crafted packets to the server.

Microsoft recommended that users block access to Port 445 to protect against the exploitation of CVE-2022-35804. However, only certain versions of Windows 11 are vulnerable to this issue.

Talos would also like to highlight eight important vulnerabilities that Microsoft considers to be “more likely” to be exploited:

A complete list of all the vulnerabilities Microsoft disclosed this month is available on its update page.

In response to these vulnerability disclosures, Talos is releasing a new Snort rule set that detects attempts to exploit some of them. Please note that additional rules may be released at a future date and current rules are subject to change pending additional information. Cisco Secure Firewall customers should use the latest update to their ruleset by updating their SRU. Open-source Snort Subscriber Rule Set customers can stay up to date by downloading the latest rule pack available for purchase on Snort.org.

The rules included in this release that protect against the exploitation of many of these vulnerabilities are 60371 - 60380, 60382 - 60384, 60386 and 60387. There are also Snort 3 rules 300233 - 300239.