December 2025 Critical CVE Round Up
December 2025 closed out the year with a surge of critical vulnerabilities impacting enterprise environments, modern application frameworks, and widely deployed security infrastructure. This month featured multiple zero-day vulnerabilities, CVSS 10.0 flaws, and confirmed active exploitation, reinforcing the need for proactive patch management and hands-on defensive readiness.
This December 2025 CVE roundup highlights the most serious enterprise security vulnerabilities, explains how threat actors are exploiting them, and outlines practical mitigation priorities for security teams.
Why December’s CVEs Matter
The attack surface for modern organizations continues to expand as attackers shift focus toward frontend frameworks, identity systems, and core enterprise platforms. December’s disclosures show how quickly vulnerabilities can move from advisory to widespread exploitation, often within days.
Several of the remote code execution vulnerabilities disclosed this month were actively abused to deploy malware or bypass authentication controls, emphasizing the growing sophistication of coordinated exploitation campaigns.
Top December 2025 Vulnerabilities Security Teams Must Prioritize
1. React2Shell – React Server Components RCE (CVE-2025-55182)
Impact: Unauthenticated Remote Code Execution
Severity: Critical (CVSS 10.0)
Status: Actively exploited zero-day
React2Shell represents one of the most severe remote code execution vulnerabilities of 2025. Affecting React Server Components, this flaw allows unauthenticated attackers to execute arbitrary code on vulnerable servers.
Shortly after disclosure, multiple threat actors exploited the vulnerability to enable malware deployment, including MINOCAT, HISONIC, and XMRIG.
Why it matters:
CVSS 10.0 with no authentication required
Rapid exploitation following disclosure
Impacts modern enterprise web applications
Enables full server compromise and persistence
Mitigation: Patch affected React deployments immediately and monitor for suspicious process execution or outbound traffic.
2. Microsoft Office Preview Pane RCE (CVE-2025-62554, CVE-2025-62557)
Impact: Remote Code Execution
Severity: Critical
Attack Vector: Email preview pane
Research: CrowdStrike
These Microsoft Office vulnerabilities arise from type confusion and use-after-free flaws. They enable attackers to execute code simply by rendering a malicious document—often through the email preview pane.
Why it matters:
Ideal for phishing-based exploitation
Minimal user interaction required
Common entry point for broader enterprise attacks
Frequently chained with privilege escalation vulnerabilities
Mitigation: Apply December Office patches and strengthen email security controls.
3. Windows Cloud Files Mini Filter Driver UAF (CVE-2025-62221)
Impact: Privilege Escalation
Severity: High
Status: Actively exploited
This use-after-free vulnerability affects the Windows Cloud Files Mini Filter Driver and is already seeing real-world exploitation. Microsoft issued a priority fix, highlighting the elevated risk.
Why it matters:
Enables post-compromise privilege escalation
Commonly chained with phishing or browser exploits
Expands attacker access across enterprise endpoints
Mitigation: Prioritize patching and monitor endpoint telemetry for suspicious elevation activity.
4. FortiGate Authentication Bypass (CVE-2025-59718, CVE-2025-59719)
Impact: Authentication bypass
Severity: Critical
Affected Systems: FortiGate appliances
Observed Activity: Malicious SSO login attempts (Arctic Wolf)
These flaws allow attackers to bypass authentication controls on FortiGate devices, enabling unauthorized access through compromised SSO workflows.
Why it matters:
Internet-facing infrastructure at high risk
Undermines perimeter trust models
Enables lateral movement and persistence
Part of a broader trend targeting network security appliances
Mitigation: Patch immediately, audit authentication logs, and restrict management interface exposure.
5. React 19 Vulnerabilities (CVE-2025-55184, CVE-2025-67779, CVE-2025-55183)
Impact: Denial of Service & Source Code Exposure
Severity: High / Critical
Research: OX Security
These React 19 vulnerabilities—distinct from React2Shell—introduce denial-of-service conditions and unintended source code exposure.
Why it matters:
Source code exposure increases future exploitability
DoS impacts application availability and reliability
Highlights increasing attacker interest in frontend frameworks
Mitigation: Update React 19 dependencies and review exposed application endpoints.
Prioritization Strategy for Enterprise Security Teams
Patch actively exploited vulnerabilities first
React2Shell (CVE-2025-55182)
Windows Cloud Files Mini Filter Driver (CVE-2025-62221)
Secure common initial access vectors
Email-based RCEs
Browser and document rendering paths
Harden identity and perimeter systems
FortiGate authentication workflows
VPN and SSO configurations
Reduce overall attack surface
Patch application frameworks
Enforce least privilege and outbound filtering
December 2025 underscored how quickly critical vulnerabilities can escalate into widespread exploitation. From zero-day vulnerabilities in React to authentication bypass flaws in enterprise firewalls, attackers continue to exploit gaps across the modern attack surface.
Staying ahead requires more than tracking advisories. It demands hands-on experience with exploitation techniques, detection methods, and real-world mitigation workflows. Understanding how these vulnerabilities are abused in practice is essential for effective defense.
INE’s hands-on cybersecurity training equips professionals with the skills needed to identify, analyze, and mitigate enterprise security vulnerabilities like those highlighted in this December 2025 CVE roundup.
Strengthen your defenses. Reduce risk. Train with INE.
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