92% of worldwide Microsoft Exchange IPs are now patched or mitigated
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2021-26855 | Unauthenticated SSRF/RCE in Microsoft Exchange Server (ProxyLogon) CVE-2021-26855 is a server-side request forgery flaw (CWE-918) in Microsoft Exchange Server that allows an unauthenticated remote attacker to send specially crafted HTTP requests and have the Exchange server process them as itself, disclosing sensitive session information. When chained with sibling Exchange flaws (the 'ProxyLogon' chain), it yields authentication bypass and arbitrary file write, escalating to full remote code execution with SYSTEM-level privileges on the on-premises Exchange server. Any organization running an affected on-premises Exchange server reachable over HTTP/HTTPS (typically outbound webmail) is exposed; Exchange Online was not affected. Exploitation is confirmed in the wild at large scale: the flaw was mass-exploited beginning in early 2021 (notably by the HAFNIUM group), is on the CISA KEV with documented ransomware use, and has a maximum EPSS score of 100% (100th percentile), despite no public PoC listing. Do: Apply the vendor's March 2021 Exchange security updates (or later cumulative updates) immediately, per the CISA required action; until patched, limit Exchange (ECP/OWA) exposure to the internet via firewall/VPN rules. Hunt for compromise: review IIS logs for unrecognized authenticated activity against FrontEnd HttpProxy endpoints, and check for malicious files or webshells under inetpub\wwwroot\aspnet_client, given the known ransomware use. | 9.1 group max | 100% | KEV ransomware PoC ×4 |
| masshundreds of thousands of on-premises deployments; tens of thousands of internet-exposed Exchange servers |
Full article356 words · extracted from securityaffairs.com · click to collapse
Microsoft revealed that 92% of all on-premises Microsoft Exchange servers exposed online affected by the ProxyLogon vulnerabilities are now patched.
On March 2nd, Microsoft released emergency out-of-band security updates that address four zero-day issues collectively tracked as ProxyLogon (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065) in all supported Microsoft Exchange versions that are actively exploited in the wild.
At the time of the release of the security patches, experts estimated that a total of 400,000 Internet-connected Microsoft Exchange servers were affected by the ProxyLogon vulnerabilities. A week later, more than 100,000 installs were still unpatched, while on March 14th, the number of unpatched servers was around 82,000.
“To illustrate the scope of this attack and show the progress made in updating systems, we’ve been working with RiskIQ. Based on telemetry from RiskIQ, we saw a total universe of nearly 400,000 Exchange servers on March 1. By March 9 there were a bit more than 100,000 servers still vulnerable.” reads the post published by Microsoft. “That number has been dropping steadily, with only about 82,000 left to be updated. We released one additional set of updates on March 11, and with this, we have released updates covering more than 95% of all versions exposed on the Internet.”
According to data collected by RiskIQ, the number of unpatched systems is less than 30,000, Microsoft also announced that 92% of worldwide Exchange IPs are now patched or mitigated.
Our work continues, but we are seeing strong momentum for on-premises Exchange Server updates:
— Security Response (@msftsecresponse) March 22, 2021
• 92% of worldwide Exchange IPs are now patched or mitigated.
• 43% improvement worldwide in the last week. pic.twitter.com/YhgpnMdlOX
Over the last weeks, Microsoft released other security updates, including ProxyLogon patches for unsupported Microsoft Exchange versions and On-premises Mitigation Tool (EOMT) tool to fix ProxyLogon issues.
The IT giant also updated Microsoft Defender Antivirus to protect unpatched Exchange servers from ProxyLogon attacks.
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Text extracted automatically; images, tables and formatting may be missing. Original: https://securityaffairs.com/115896/security/microsoft-exchange-patched.html