The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has urged federal agencies to patch the recent React2Shell vulnerability by December 12, 2025, amid reports of widespread exploitation.
The critical vulnerability, tracked as CVE-2025-55182 (CVSS score: 10.0), affects the React Server Components (RSC) Flight protocol. The underlying cause of the issue is an unsafe deserialization that allows an attacker to inject malicious logic that the server executes in a privileged context. It also affects other frameworks, including Next.js, Waku, Vite, React Router, and RedwoodSDK.
"A single, specially crafted HTTP request is sufficient; there is no authentication requirement, user interaction, or elevated permissions involved," Cloudforce One, Cloudflare's threat intelligence team, said. "Once successful, the attacker can execute arbitrary, privileged JavaScript on the affected server."
Since its public disclosure on December 3, 2025, the shortcoming has been exploited by multiple threat actors in various campaigns to engage in reconnaissance efforts and deliver a wide range of malware families.
The development prompted CISA to add it to its Known Exploited Vulnerabilities catalog last Friday, giving federal agencies until December 26 to apply the fixes. The deadline has since been revised to December 12, 2025, an indication of the severity of the incident.
