CISA Issues Emergency Directive on In-the
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 | 100% | KEV ransomware PoC ×4 |
| masshundreds of thousands of on-premises deployments; tens of thousands of internet-exposed Exchange servers |
Full article344 words · extracted from thehackernews.com · click to collapse
Ravie LakshmananMar 04, 2021
Following Microsoft's release of out-of-band patches to address multiple zero-day flaws in on-premises versions of Microsoft Exchange Server, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) has issued an emergency directive warning of "active exploitation" of the vulnerabilities.
The alert comes on the heels of Microsoft's disclosure that China-based hackers were exploiting unknown software bugs in Exchange server to steal sensitive data from select targets, marking the second time in four months that the U.S. has scrambled to address a widespread hacking campaign believed to be the work of foreign threat actors.
While the company mainly attributed the campaign to a threat group called HAFNIUM, Slovakian cybersecurity firm ESET said it found evidence of CVE-2021-26855 being actively exploited in the wild by several cyber espionage groups, including LuckyMouse, Tick, and Calypso targeting servers located in the U.S., Europe, Asia, and the Middle East.
Researchers at Huntress Labs have also sounded the alarm about mass exploitation of Exchange servers, noting that over 350 web shells have been discovered across approximately 2,000 vulnerable servers.
"Among the vulnerable servers, we also found over 350 web shells — some targets may have more than one web shell, potentially indicating automated deployment or multiple uncoordinated actors," Huntress senior security researcher John Hammond said. "These endpoints do have antivirus or EDR solutions installed, but this has seemingly slipped past a majority of preventative security products."
The latest development indicates a much larger spread that extends beyond the "limited and targeted" attacks reported by Microsoft earlier this week.
It's not clear if any U.S. government agencies have been breached in the campaign, but the CISA directive underscores the urgency of the threat.
Strongly urging organizations to apply the patches as soon as possible, the agency cited the "likelihood of widespread exploitation of the vulnerabilities after public disclosure and the risk that federal government services to the American public could be degraded."
Found this article interesting? Follow us on Google News, Twitter and LinkedIn to read more exclusive content we post.
Text extracted automatically; images, tables and formatting may be missing. Original: https://thehackernews.com/2021/03/cisa-issues-emergency-directive-on-in.html