China-Linked Silk Typhoon Expands Cyber Attacks to IT Supply Chains for Initial Access

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.

Apache Log4j2, an extremely widely used Java logging library, fails to protect its JNDI lookup feature against attacker-controlled JNDI-related endpoints (CWE-20, CWE-502), so crafted text processed by the logger causes the Java runtime to fetch and load attacker-supplied objects, leading to remote code execution. The flaw is triggered whenever attacker-controlled input reaches the logging API and is parsed for JNDI lookups, a pattern common in web servers and enterprise Java applications that log user-supplied fields such as headers or form values. Successful exploitation yields arbitrary code execution under the privileges of the affected application, giving attackers a foothold for lateral movement, data theft, and ransomware deployment. Any Java application or product that ships or bundles an affected Apache Log4j2 release is exposed, making this one of the most broadly deployed vulnerabilities ever disclosed. Exploitation is confirmed in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2021-12-10 with known ransomware use, and EPSS assigns a 100% probability of exploitation within 30 days.

Do: Inventory all Java applications and dependencies for Apache Log4j2 and apply the vendor's patched updates, or remove affected assets from the network, as required by CISA's KEV catalog. Where updates are not yet available, use the temporary mitigations in CISA's ED-22-02 recommended-mitigation guidance, such as disabling message lookups, only until patches are applied. Prioritize internet-facing and business-critical systems and hunt for exploitation activity given known ransomware use.

CVE-2023-3519 is a critical (CVSS 9.8) unauthenticated remote code execution flaw caused by improper code-injection handling (CWE-94) in Citrix NetScaler ADC and NetScaler Gateway. A remote attacker with no credentials can trigger it by sending crafted requests to an appliance configured as a Gateway (VPN/ICA proxy/RDP proxy) or AAA authentication virtual server, gaining arbitrary code execution on the appliance. Exploitation typically yields a foothold behind the VPN edge — access to internal networks, credential theft, and follow-on activity such as espionage or ransomware deployment. Any organization running unpatched NetScaler ADC/Gateway appliances, especially internet-facing remote-access endpoints, is affected; NetScaler is one of the most widely deployed enterprise VPN/ADC platforms. Exploitation is confirmed in the wild: the flaw was added to CISA's KEV on 2023-07-19 with known ransomware use, EPSS estimates a 99.7% exploitation probability, and researchers have linked activity to China-nexus espionage (Silk Typhoon) and ransomware operations.

Do: Immediately upgrade internet-facing NetScaler ADC/Gateway appliances to the fixed builds in Citrix's advisory (14.1-8.50+, 13.1-49.13+, 13.0-82.45+, 12.1-55.300+, including FIPS/NDcPP equivalents) — per CISA KEV, apply these mitigations or discontinue use if patching is unavailable. Confirm whether each appliance is configured as a Gateway or AAA virtual server (only those are affected), and hunt for compromise — unexpected configuration changes, unfamiliar accounts, webshells, or anomalous VPN sessions — rotating credentials on any suspected compromise.

Palo Alto Networks PAN-OS contains a command injection flaw (CWE-77, with improper input validation per CWE-20) in its GlobalProtect feature, allowing an unauthenticated attacker to execute arbitrary operating-system commands with root privileges on the affected firewall. The flaw is triggered through the GlobalProtect interface, which in most deployments is reachable from untrusted networks, so no valid user credentials or prior access are required. Successful exploitation yields full root control of the firewall, the most powerful position in a network perimeter, enabling traffic interception, configuration tampering, and use as a foothold for further compromise. All PAN-OS firewalls running affected releases with the GlobalProtect feature are exposed; CISA added the issue to the KEV catalog on 2024-04-12 with ransomware use noted, and EPSS puts the 30-day exploitation probability at 100% (100th percentile). No public proof-of-concept is recorded in the source data, but confirmed in-the-wild exploitation makes patching urgent.

Do: Apply the PAN-OS patches released in Palo Alto Networks' bulletin according to its published patch schedule, prioritizing internet-facing firewalls. Until patched, enable the vendor's Threat Prevention signatures as required by CISA KEV, restrict exposure of the GlobalProtect interface to trusted sources where possible, and review logs and device configuration for signs of compromise given confirmed exploitation with known ransomware use.

CVE-2025-0282 is a stack-based buffer overflow (CWE-121) in Ivanti Connect Secure, Policy Secure, and ZTA Gateways, reachable by unauthenticated network input. An attacker can trigger it remotely by sending crafted, unauthenticated traffic to a vulnerable gateway, overwriting stack memory and gaining code execution under the appliance's context. Successful exploitation yields unauthenticated remote code execution on the device, giving the attacker control of the VPN/secure-access gateway and a foothold into the protected network. Organizations running any of the affected Ivanti secure-access products are exposed; the source data specifies no version ranges, so defenders should consult Ivanti's advisory for exact affected and fixed releases. The flaw is being actively exploited: it was added to CISA KEV on 2025-01-08 with known ransomware use, and EPSS assigns a 100% probability of exploitation within 30 days (100th percentile), despite no public PoC being known.

Do: Apply the patched releases identified in Ivanti's advisory and follow CISA's required action: hunt for signs of compromise, remediate if indicators are found, and apply updates before returning any device to service. Because exploitation is active and ransomware use is known, treat any appliance that was internet-reachable before patching as potentially compromised (check integrity, rotate credentials). Exact fixed versions were not included in the source data, so verify the correct update path for your branch (including older Connect Secure/Policy Secure releases) against Ivanti's bulletin.