Microsoft Patch Tuesday for April 2023 — Snort rules and prominent vulnerabilities
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2022-37969 | Out-of-bounds write flaw in Microsoft Windows CLFS driver enables privilege escalation The Windows Common Log File System (CLFS) driver contains an input-validation flaw (CWE-20) that leads to an out-of-bounds write (CWE-787), allowing an attacker who already has a foothold or local access on a system to escalate privileges. It is triggered when the driver processes malformed or specially crafted common log file data, rather than via a remote network request on its own. Successful exploitation yields elevated (typically SYSTEM-level) privileges, giving the attacker full control of the host and making the bug a common post-exploitation link in ransomware chains. CISA lists the affected product broadly as 'Microsoft Windows', so essentially all Windows installations current at the time of disclosure were in scope. The flaw is confirmed exploited in the wild: CISA added it to the KEV catalog on 2022-09-14 with known ransomware use, EPSS puts 30-day exploitation probability at 28.3% (98th percentile), and no public PoC is known. Do: Apply Microsoft's September 2022 (or later) cumulative updates to every Windows host per vendor instructions, prioritizing endpoints and servers exposed for user or remote access. Because this is a local privilege escalation, treat it as a post-exploitation risk: also harden and patch initial-access surfaces (RDP, VPN, other exposed services) and hunt for signs of compromise such as unexpected SYSTEM-spawned processes or anomalous activity involving clfs.sys. Ransomware operators are known to use this bug, so remediation should be treated as urgent. | 7.8 | 28% | KEV ransomware |
| mass>1 billion Windows devices (essentially all Windows installations at the time of disclosure; exploitation requires an existing local foothold) | |
| CVE-2023-21554 | Microsoft Message Queuing (MSMQ) Remote Code Execution Vulnerability Microsoft Message Queuing (MSMQ) Remote Code Execution Vulnerability NVD description · AI analysis pending | 9.8 | 95% |
| — | ||
| CVE-2023-28250 | Windows Pragmatic General Multicast (PGM) Remote Code Execution Vulnerability Windows Pragmatic General Multicast (PGM) Remote Code Execution Vulnerability NVD description · AI analysis pending | 9.8 group max | 2% |
| — | ||
| CVE-2023-28231 +1 in the same advisory: …28240 | DHCP Server Service Remote Code Execution Vulnerability DHCP Server Service Remote Code Execution Vulnerability NVD description · AI analysis pending | 8.8 | 37% |
| — | ||
| CVE-2023-28252 | Heap Overflow in Microsoft Windows CLFS Driver Enables Local Privilege Escalation CVE-2023-28252 is a heap-based buffer overflow (CWE-122) in the Microsoft Windows Common Log File System (CLFS) driver that allows privilege escalation. The flaw is triggered when the kernel's CLFS driver processes malformed or maliciously crafted log file data, corrupting heap memory; an attacker who can already run code on a target system (e.g., a low-privileged user or an attacker chained with another flaw such as a remote code execution bug) can leverage it to gain SYSTEM-level privileges. Because the CLFS driver ships with supported Windows client and server releases, essentially the entire Windows installed base is potentially exposed. The vulnerability is being actively exploited: CISA added it to the KEV catalog on 2023-04-11 with known ransomware use, and EPSS estimates a 49.0% probability of exploitation within 30 days (99th percentile). It was addressed in Microsoft's April 2023 security updates, and the required remediation action is to apply the vendor updates. Do: Apply Microsoft's April 2023 (or later) cumulative security updates to all Windows clients and servers per vendor instructions, prioritizing high-value and domain infrastructure systems given the known ransomware use; there is no public PoC or known workaround, so patching is the primary mitigation. Note that this is a local elevation-of-privilege flaw, so also hunt for prior low-privilege access or exploitation chains on hosts, and confirm remediation by checking installed update levels across the estate. | 7.8 | 49% | KEV ransomware PoC |
| masshundreds of millions of Windows devices (the CLFS driver is present across essentially all modern Windows 10/11 and Windows Server installations) | |
| CVE-2023-28291 | Raw Image Extension Remote Code Execution Vulnerability Raw Image Extension Remote Code Execution Vulnerability NVD description · AI analysis pending | 7.8 | <1% |
| — |
Full article564 words · extracted from blog.talosintelligence.com · click to collapse
Tuesday, April 11, 2023 15:28
Microsoft released its monthly round of security updates and patches today, continuing its trend of fixing zero-day vulnerabilities on Patch Tuesday.
April's security update includes one vulnerability that’s actively being exploited in the wild. There are also eight critical vulnerabilities and the remaining 90 are considered “important.”
CVE-2023-28252, an elevation of privilege vulnerability in the Windows Common Log File System Driver, is actively being exploited in the wild, according to Microsoft, though proof of concept code is not currently available. An adversary could exploit this vulnerability to gain SYSTEM privileges.
The U.S. Cybersecurity and Infrastructure Security Agency already added the vulnerability to its list of know exploited issues and urged federal agencies to patch it as soon as possible.
Microsoft disclosed a similar zero-day issue in September that could also lead to the same privileges: CVE-2022-37969. April is the third month in a row in which at least one of the vulnerabilities Microsoft released in a Patch Tuesday had been exploited in the wild prior to disclosure.
Two of the critical vulnerabilities Microsoft also patched are in the Layer 2 Tunneling Protocol: CVE-2023-28219 and CVE-2023-28220. An unauthenticated attacker could send a specially crafted connection request to a RAS server, which could lead to remote code execution on the RAS server machine. These vulnerabilities do not require any user interaction to be exploited, but the adversary would need to win a race condition to be successful.
One of the most severe issues is CVE-2023-21554, a remote code execution vulnerability in the Microsoft Message queuing system. Microsoft considers exploitation of this vulnerability to be “more likely,” and it received a CVSS severity score of 9.8 out of 10. Users who want to check to see if they’re being targeted by the exploitation of this vulnerability can run a check to see if there’s a service named “Message Queuing” on their machine, and if TCP port 1801 is listening on the machine.
CVE-2023-28231, a remote code execution vulnerability on the DHCP server service, is also considered “more likely” to be exploited. An attacker could exploit this vulnerability by sending a specially crafted RCP call to the targeted DHCP server. However, the adversary first must gain access to the restricted network.
There are four other critical vulnerabilities, though Microsoft considers them “less likely” to be exploited:
- CVE-2023-28232: Windows Point-to-Point Tunneling Protocol remote code execution vulnerability
- CVE-2023-28240: Windows Network Load Balancing remote code execution vulnerability
CVE-2023-28250: Windows Pragmatic General Multicast (PGM) remote code execution vulnerability - CVE-2023-28291: Raw Image Extension remote code execution vulnerability
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 61606, 61607 and 61613 - 61620. There are also Snort 3 rules 300496, 300499 and 300500.
Text extracted automatically; images, tables and formatting may be missing. Original: https://blog.talosintelligence.com/microsoft-patch-tuesday-for-april-2023/