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CVE-2021-31207 is a security feature bypass in Microsoft Exchange Server, classified as an unrestricted file-write issue (CWE-434) that lets an attacker bypass intended restrictions and write files of their choosing to the server. It is the final bug in the ProxyShell chain: chained with the autodiscover SSRF and PowerShell backend elevation flaws, it allows an unauthenticated attacker to reach the Exchange PowerShell API, write arbitrary files such as an ASPX webshell, and execute code with SYSTEM privileges. A successful attacker gains full control of the on-premises Exchange server, including mailbox access, stolen credentials, and a foothold for lateral movement; the bug has been used to deploy ransomware and keyloggers. On-premises deployments of Microsoft Exchange Server (2013, 2016, and 2019 per vendor advisories) are affected, while Exchange Online/cloud mailboxes are not. Exploitation is essentially certain and ongoing: the flaw is in CISA's KEV (added 2021-11-03) with known ransomware use, public ProxyShell PoC/exploit code is available, and EPSS puts the 30-day exploitation probability at 99.8%.

Do: Apply Microsoft's July 2021 security updates for Exchange Server 2013, 2016, and 2019 (or any later security/cumulative update) per vendor instructions, and restrict untrusted access to Exchange's autodiscover and PowerShell endpoints. Hunt for ASPX webshells under the Exchange FrontEnd directories and review IIS logs for autodiscover.json requests chaining PowerShell, since many servers were compromised before patching. Given known ransomware use and KEV listing, treat any server that was unpatched or internet-exposed during the exploitation window as potentially compromised.

Microsoft Exchange Server contains a server-side request forgery (SSRF, CWE-918) in the Autodiscover service that unauthenticated remote attackers can reach over HTTP. This flaw is the first stage of the widely documented 'ProxyShell' chain, in which the SSRF is combined with privilege escalation and an arbitrary file write in the Exchange PowerShell backend to achieve unauthenticated remote code execution on the server. An attacker who successfully exploits it gains the ability to run code on the Exchange server, and ransomware operators (e.g., Cuba ransomware) leveraged this chain to deploy payloads. Organizations running on-premises Microsoft Exchange Server (2013, 2016, and 2019 per the vendor's advisories) are affected; hosted Exchange Online is a separately managed cloud service. Exploitation is confirmed in the wild: CISA added the flaw to the KEV catalog on 2021-11-03 with known ransomware use, and EPSS assigns it a 100% probability of exploitation within 30 days (100th percentile).

Do: Apply Microsoft's July 2021 (or later) Exchange Server security updates, which include the ProxyShell fixes, to all on-premises servers. If patching is delayed, restrict internet access to the Autodiscover/EWS frontend endpoints and consider the URL Rewrite mitigation Microsoft published for ProxyShell. Given the KEV listing and known ransomware use, treat internet-facing, unpatched Exchange servers as potentially compromised and hunt for webshells, unusual Exchange processes, and suspicious account or mailbox activity.

CVE-2023-26360 is an improper access control flaw (CISA categorizes it as deserialization of untrusted data) in Adobe ColdFusion 2018 (Update 15 and earlier) and ColdFusion 2021 (Update 5 and earlier). It can be triggered over the network with no authentication and no user interaction. A successful attacker achieves arbitrary code execution in the context of the current user, giving them full control of the ColdFusion server. Any organization running the affected ColdFusion versions is exposed, particularly those with instances reachable from the internet; public reporting confirms exploitation in the wild, including a breach of federal agency servers. The flaw was added to CISA's Known Exploited Vulnerabilities Catalog on 2023-03-15, has a public proof-of-concept, and carries a 97.3% EPSS probability of exploitation within 30 days.

Do: Apply Adobe's updates per vendor instructions, upgrading ColdFusion 2018 beyond Update 15 and ColdFusion 2021 beyond Update 5. Because exploitation is unauthenticated and confirmed in the wild (including against a federal agency), prioritize patching internet-facing servers, restrict ColdFusion endpoints to trusted networks in the interim, and hunt for signs of compromise such as web shells, unexpected processes, and suspicious connections (reported activity includes malicious web shell use). Organizations that cannot patch immediately should at minimum limit exposure and monitor for exploitation attempts.