Security vulnerabilities are a common occurrence in managing any business’s organizational security. The prompt patching and remediation of any new vulnerabilities are critical to reducing the outside attack surface. Netizen’s Security Operations Center (SOC) has compiled five critical vulnerabilities from December that should be immediately patched or addressed if present in your environment. Detailed writeups below:
CVE-2025-20393
CVE-2025-20393 is a critical zero-day vulnerability impacting Cisco Secure Email Gateway appliances running AsyncOS and Cisco Secure Email and Web Manager. Cisco initially disclosed the issue after detecting real-world attacks linked to a China-nexus threat actor (tracked as UAT-9686). The flaw allows an unauthenticated remote attacker to gain command execution on vulnerable appliances with root-level privileges, giving full control over the underlying operating system. Public reporting indicates targeted exploitation began before disclosure, with attackers focusing on internet-exposed systems used in enterprise and government environments. The vulnerability carries a CVSS v3.1 base score of 10.0, reflecting the fact that no credentials, user interaction, or elevated privileges are required for exploitation.
Victims observed behavior consistent with reconnaissance, persistence activity, and execution of attacker-controlled payloads. The attack path appears conditional, depending on specific feature configurations present on affected appliances. Cisco has not yet released full technical details, but the company confirmed ongoing investigation and acknowledged active exploitation. CISA added CVE-2025-20393 to the Known Exploited Vulnerabilities (KEV) catalog on December 18, 2025, directing federal agencies to remediate as a priority. Security researchers also noted coordinated password-spraying activity against Cisco VPN gateways during the same period, suggesting broader targeting of Cisco infrastructure by the same actor set.
Given full system compromise is possible, organizations should isolate impacted appliances from the internet where feasible, apply Cisco’s interim guidance, monitor for unauthorized admin accounts and modifications, and review logs and outbound connections for evidence of compromise. Patching should be treated as urgent once Cisco releases a permanent fix, as continued exposure presents a significant risk to email security infrastructure and downstream systems integrated with these gateways.
CVE-2025-55182
CVE-2025-55182, widely referred to as React2Shell, is a critical pre-authentication remote code execution vulnerability affecting React Server Components (RSC) in versions 19.0.0, 19.1.0, 19.1.1, and 19.2.0. The affected packages include react-server-dom-parcel, react-server-dom-turbopack, and react-server-dom-webpack, and the risk extends to frameworks that embed these components such as Next.js and React Router implementations that expose server functions. The flaw stems from unsafe deserialization logic in the RSC Flight protocol. Server Function endpoints accept serialized request payloads sent over HTTP and attempt to reconstruct React objects and callable functions on the server. The vulnerable code trusts the inbound serialized data without hard boundaries around what is allowed during deserialization. An attacker who can reach an exposed RSC endpoint can submit a crafted payload that injects malicious objects into the deserializer so that attacker-controlled values are interpreted as executable server logic.
From an attack-path standpoint, this is particularly dangerous because the weakness sits before any authentication checks. The typical exploit flow involves the attacker identifying a server function endpoint that processes RSC Flight payloads, then sending a single HTTP request containing a maliciously structured binary or JSON-encoded Flight stream. During processing, the server runtime attempts to resolve and invoke the referenced functions and data structures. The crafted payload manipulates this behavior so that arbitrary Node.js execution occurs in the server process context. No credentials are required, and there is no need to trick an end user into clicking anything. Default installations of affected versions are exposed if server components are reachable from the internet, which means routine application deployments may already present a viable target surface. Because the execution path occurs inside the application runtime rather than an external interpreter, traditional web security controls often fail to block the attack, and in many observed cases both Linux- and Windows-based deployments were impacted, including containerized environments.
Successful exploitation grants the attacker the ability to run code with the privileges of the application service account. That access can be used to deploy webshells, steal secrets, pivot deeper into cloud environments, or stage ransomware. Public reporting has confirmed active exploitation by advanced threat actors shortly after disclosure, and CISA added the CVE to the Known Exploited Vulnerabilities catalog. The vulnerability is rated at the maximum CVSS 10.0 level due to the combination of remote reachability, low attack complexity, lack of authentication, and the severe confidentiality, integrity, and availability impact.
Organizations running affected React Server Component versions or frameworks that consume the vulnerable serialization libraries should assume exposure if endpoints are internet-accessible. The immediate priority is to upgrade to the patched releases provided by the React project and any downstream framework vendors, validate that mitigations are deployed across all environments including staging systems, and review server logs and runtime telemetry for suspicious RSC requests or unexpected server function invocation behavior dating back to early December 2025. Given the pre-auth nature of the flaw and the breadth of affected ecosystems, this vulnerability represents a material operational risk until completely remediated.
CVE-2025-6218
CVE-2025-6218 is a high-severity directory traversal flaw in RARLAB WinRAR that can lead to remote code execution. The weakness sits in the way WinRAR handles file paths inside archive files. A malicious archive can include specially crafted paths that escape the expected extraction directory and write files elsewhere on the system. If a user opens or interacts with one of these archives — such as by downloading it from a malicious site or opening it from email — the attacker-controlled files can be written and executed in the context of the current user. This vulnerability has been confirmed as exploited in the wild and has been added to the CISA Known Exploited Vulnerabilities catalog, underscoring its operational relevance to defenders.
The practical impact depends on the user’s privileges and the presence of additional controls, but code execution through a trusted file archiver presents clear risk for both consumer and enterprise environments. Organizations using WinRAR should apply the vendor’s fixed release and review systems for signs of anomalous archive activity linked to suspicious paths or unexpected file placement. Since exploitation requires only basic user interaction and attackers routinely weaponize archive vulnerabilities for phishing-style delivery, this CVE warrants prompt remediation and user awareness..
CVE-2025-14733
CVE-2025-14733 is a critical out-of-bounds write flaw in WatchGuard Fireware OS that allows a remote, unauthenticated attacker to execute arbitrary code. The weakness affects Fireware deployments that use IKEv2 for Mobile User VPN or Branch Office VPN when the VPN is configured with a dynamic gateway peer. Impacted versions include 11.10.2 through 11.12.4_Update1, 12.0 through 12.11.5, and 2025.1 through 2025.1.3. Because exploitation requires only network access to a vulnerable device and no authentication, compromised systems can be taken over completely, exposing internal networks, VPN credentials, and downstream assets. This vulnerability has been confirmed as exploited in the wild and is listed in CISA’s Known Exploited Vulnerabilities catalog, signaling that active threat actors are targeting unpatched Firebox devices.
Organizations should update to the patched Fireware releases provided by WatchGuard and review VPN configurations that rely on IKEv2 with dynamic peers. Since exploitation grants full device compromise, affected firewalls should be treated as potentially hostile if they were exposed before patching, with incident response procedures applied as needed. Monitoring for anomalies on VPN tunnels, unexpected administrative logins, and configuration changes can help identify prior malicious activity.
CVE-2025-62221
CVE-2025-62221 is a local privilege escalation vulnerability in the Windows Cloud Files Mini Filter Driver caused by a use-after-free condition. A logged-in attacker with limited privileges can trigger memory corruption and gain full control of the system, impacting confidentiality, integrity, and availability. Microsoft confirmed that this flaw was exploited before a patch was released, and it was one of the most notable fixes in the December 2025 Patch Tuesday update cycle. Although exploitation requires local access, the vulnerability is valuable for threat actors who already have a foothold through phishing, malware, or lateral movement, since it allows them to elevate to administrator or SYSTEM.
Given the confirmed in-the-wild exploitation, organizations should prioritize deployment of the December 2025 cumulative updates across all supported Windows platforms. Security teams should also review endpoint telemetry for signs of privilege escalation activity such as unexplained SYSTEM-level processes tied to user accounts, abnormal driver or filter activity, or privilege escalation behavior following initial access events. Hardening privileged access procedures, reducing local admin footprint, and monitoring for persistence mechanisms can help contain the blast radius if this vulnerability has already been used as part of a broader intrusion.
How Can Netizen Help?
Netizen ensures that security gets built-in and not bolted-on. Providing advanced solutions to protect critical IT infrastructure such as the popular “CISO-as-a-Service” wherein companies can leverage the expertise of executive-level cybersecurity professionals without having to bear the cost of employing them full time.
We also offer compliance support, vulnerability assessments, penetration testing, and more security-related services for businesses of any size and type.
Additionally, Netizen offers an automated and affordable assessment tool that continuously scans systems, websites, applications, and networks to uncover issues. Vulnerability data is then securely analyzed and presented through an easy-to-interpret dashboard to yield actionable risk and compliance information for audiences ranging from IT professionals to executive managers.
Netizen is an ISO 27001:2013 (Information Security Management), ISO 9001:2015, and CMMI V 2.0 Level 3 certified company. We are a proud Service-Disabled Veteran-Owned Small Business that is recognized by the U.S. Department of Labor for hiring and retention of military veterans.
Looking for expert guidance to secure, automate, and streamline your IT infrastructure and operations? Start the conversation today.
Netizen Blog and News 
Leave a comment