Citrix, VMware, and Atlassian Hit with Critical Flaws — Patch ASAP!

Atlassian Confluence Data Center and Server contain an unauthenticated OGNL template injection vulnerability (CWE-74) in which attacker-controlled input is evaluated by the application as an OGNL expression. A remote, unauthenticated attacker can trigger the flaw by sending a crafted HTTP request that injects OGNL expressions, which the server then executes. Successful exploitation leads to remote code execution on the host running Confluence, giving the attacker control of the system without any credentials. Any organization running self-hosted Confluence Data Center or Server is potentially affected — the available data does not specify version ranges, so operators should consult Atlassian's advisory — with internet-facing instances at highest risk. Exploitation is active: the flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2024-01-24 with known ransomware use, and EPSS assigns it a 100% probability of exploitation within 30 days (100th percentile).

Do: Patch to the fixed release specified in Atlassian's advisory immediately, prioritizing internet-exposed instances, since the flaw is in CISA's KEV with known ransomware use and carries a 100% EPSS. If patching is not immediately possible, apply the vendor's mitigations per the KEV required action — or discontinue/restrict use — for example by limiting unauthenticated access to Confluence from the internet. Review Confluence access and application logs for anomalous unauthenticated requests and indicators of command execution or ransomware activity.

Aria Automation contains a Missing Access Control vulnerability. An authenticated malicious actor may exploit this vulnerability leading to unauthorized access to remote organizations and workflows.

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.

Citrix NetScaler ADC and NetScaler Gateway appliances contain a buffer overflow (CWE-119) that leaks sensitive information from device memory when the appliance is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, or RDP Proxy) or as an AAA virtual server. A remote attacker who can reach such a configuration can trigger the overflow and read memory contents, harvesting sensitive data such as session tokens (a technique that enables session hijacking which can bypass multi-factor authentication). Any organization running an affected NetScaler ADC or Gateway appliance in these configurations is exposed, with appliances deployed as VPN or access gateways being the primary concern. Exploitation is confirmed in the wild: the flaw was added to CISA's KEV catalog on 2023-10-18 with known ransomware use and a 100% EPSS exploitation probability, although no public proof-of-concept is known at this time. Because tokens stolen from memory can remain valid even after patching, responders must terminate all active and persistent sessions as part of remediation.

Do: Upgrade affected appliances to the patched builds cited in Citrix's advisory, then immediately kill all active and persistent ICA/AAA sessions per the vendor instructions, since patching alone does not invalidate session tokens attackers may have already stolen. If patching is not immediately possible, discontinue use of the affected Gateway/AAA configurations as CISA directs. Given known ransomware abuse, also hunt for signs of exploitation such as logins from unexpected sources, anomalous session reuse, or suspicious mailbox changes, and reset credentials for potentially exposed accounts.

CVE-2023-6548 is a code injection flaw (CWE-94) in the management interface of Citrix NetScaler ADC and NetScaler Gateway that allows remote code execution. It is triggered when an attacker who can reach the appliance's NSIP, CLIP, or a SNIP with management interface access authenticates with valid low-privileged credentials and sends crafted input that the appliance turns into executable code. Successful exploitation yields authenticated remote code execution in the context of the management interface, with high impact on the confidentiality, integrity, and availability of the appliance. Affected organizations are those running Citrix NetScaler ADC or NetScaler Gateway appliances, particularly deployments whose management interfaces are reachable from less-trusted networks or shared with low-privileged users. The flaw is being exploited in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2024-01-17 and urged immediate action, though no public proof-of-concept code is known and EPSS currently estimates a ~3.2% chance of exploitation within 30 days.

Do: Upgrade affected NetScaler ADC and NetScaler Gateway appliances to the fixed builds in Citrix's security bulletin for CVE-2023-6548 (released alongside the companion CVE-2023-6546 NetScaler privilege-escalation fix), per CISA's KEV directive to apply vendor mitigations or discontinue use of the product if mitigations are unavailable. Reduce exposure by restricting management interface access on the NSIP, CLIP, and SNIPs to trusted admin networks and by removing or constraining low-privileged accounts that do not need management access. Review appliance authentication logs and configurations for unexpected logins or changes, since exploitation requires authenticated access to the management interface.