Denial-of-Service and Source Code Exposure Vulnerabilities in React Server Components
Multiple vulnerabilities have been identified in React Server Components (RSC), specifically CVE-2025-55183, CVE-2025-55184, and CVE-2025-67779, affecting several versions of react-server-dom-webpack, react-server-dom-parcel, and react-server-dom-turbopack. These vulnerabilities, discovered following the React2Shell incident, include a high-severity denial-of-service (DoS) flaw (CVE-2025-55184) caused by unsafe deserialization of structured input in the RSC Flight protocol, which can be exploited by sending specially crafted requests that trigger infinite loops or event-loop lockups on the server. The vulnerabilities also raise concerns about potential source code exposure and highlight the risk of residual flaws being discovered after major disclosures.
The React Foundation has issued advisories and patches for affected versions, and the Canadian Centre for Cyber Security has urged administrators to update impacted libraries and frameworks, including popular tools such as Next.js, Vite RSC plugin, Parcel RSC plugin, React Router RSC preview, RedwoodSDK, and Waku. No public exploits are currently available, but the vulnerabilities have a higher-than-average likelihood of exploitation, emphasizing the importance of prompt remediation and ongoing vigilance for follow-on issues after initial vulnerability disclosures.
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How this story unfolded
5 events from the most recent confirmed update back to the earliest known activity.
Canadian Centre for Cyber Security urges immediate review and patching
On 2025-12-15, the Cyber Centre published advisory AV25-834 warning that frameworks and libraries bundling React server implementations, such as Next.js, Vite RSC plugin, Parcel RSC plugin, React Router RSC preview, RedwoodSDK, and Waku, were also likely impacted. It urged organizations to review exposure and apply patches immediately.
React releases updated versions to address follow-on RSC flaws
React provided fixes for the newly disclosed vulnerabilities in versions 19.0.3, 19.1.4, and 19.2.3. Applications using React 19.0.0 through 19.2.2 were identified as affected, including deployments that had already patched for React2Shell.
React Foundation issues advisory for three React server-side CVEs
On 2025-12-11, the React Foundation published a security advisory covering CVE-2025-55183, CVE-2025-55184, and CVE-2025-67779 in react-server-dom-webpack, react-server-dom-parcel, and react-server-dom-turbopack. The advisory identified denial-of-service and source code exposure risks in affected React server-side libraries.
Additional React RSC vulnerabilities discovered during follow-on review
After React2Shell was disclosed, deeper inspection of React Server Components uncovered three additional vulnerabilities: CVE-2025-55183, CVE-2025-55184, and CVE-2025-67779. The issues introduced risks including denial of service and server-side source code exposure.
React2Shell vulnerability disclosed in React Server Components
A prior major disclosure, React2Shell (CVE-2025-55182), was publicly disclosed before the follow-on issues. Subsequent investigation into the React codebase occurred after this disclosure.
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Denial-of-Service and Source Code Exposure Vulnerabilities in React Server Components
Security researchers have identified three new vulnerabilities in React Server Components (RSC) following the recent patch for the critical React2Shell exploit. These flaws include two high-severity Denial-of-Service (DoS) vulnerabilities (CVE-2025-55184 and CVE-2025-67779) and a medium-severity Source Code Exposure vulnerability (CVE-2025-55183). The DoS vulnerabilities allow attackers to send malicious HTTP requests to Server Function endpoints, triggering infinite loops that hang the server and exhaust CPU resources, effectively taking applications offline. The source code exposure flaw enables attackers to craft HTTP requests that can leak the source code of server functions, potentially exposing hardcoded secrets or sensitive logic, though runtime secrets remain protected. The affected packages are `react-server-dom-webpack`, `react-server-dom-parcel`, and `react-server-dom-turbopack`, impacting React versions 19.0.0 through 19.2.2 and frameworks such as Next.js, Waku, and React Router. Initial patches released for these vulnerabilities were incomplete, necessitating immediate upgrades to versions 19.0.3, 19.1.4, and 19.2.3 to ensure full protection. The vulnerabilities were discovered by security researchers during attempts to bypass previous mitigations, highlighting the importance of rapid patch adoption and ongoing scrutiny of critical code paths after major disclosures. Users are strongly advised to update affected packages and monitor official channels for further security updates.
Mar 21, 2026
Critical Unauthenticated RCE Vulnerabilities in React Server Components and Next.js
A critical unauthenticated remote code execution (RCE) vulnerability, tracked as CVE-2025-55182, has been discovered in React Server Components, affecting core React packages (`react-server-dom-webpack`, `react-server-dom-parcel`, and `react-server-dom-turbopack`) in versions 19.0, 19.1.0, 19.1.1, and 19.2.0. The flaw arises from unsafe deserialization of payloads sent to React Server Function endpoints, allowing attackers to execute arbitrary code on the server without authentication. This vulnerability also impacts frameworks and bundlers that integrate React Server Components, including Next.js (assigned CVE-2025-66478), Vite, Parcel, React Router, RedwoodSDK, and Waku. Even default configurations and newly generated Next.js applications are vulnerable, and exploitation requires only a crafted HTTP request, with no developer error or special setup needed. Immediate patching is strongly advised, as the vulnerability is rated CVSS 10.0 (critical) and has been shown to be highly reliable in exploitation tests. Patched versions are available for React (19.0.1, 19.1.2, 19.2.1) and Next.js (15.0.5, 15.1.9, 15.2.6, 15.3.6, 15.4.8, 15.5.7, 16.0.7), and users are urged to upgrade all affected packages and dependencies. Some hosting providers, such as Vercel, have implemented temporary platform-level mitigations, but these are not a substitute for patching. Security researchers estimate that up to 39% of cloud environments may contain vulnerable instances, underscoring the urgency of remediation across the React and Next.js ecosystem.
Mar 21, 2026
Denial-of-Service Vulnerability in React Server Components (CVE-2025-55184)
A denial-of-service (DoS) vulnerability, tracked as CVE-2025-55184, has been identified in React Server Components (RSC) affecting versions 19.0.0 through 19.2.1 and related packages such as `react-server-dom-parcel`, `react-server-dom-turbopack`, and `react-server-dom-webpack`. The flaw arises from unsafe deserialization of payloads in the React Flight protocol, allowing specially crafted HTTP requests to trigger infinite loops or hung server states, rendering affected applications unresponsive. This issue is particularly relevant for applications using Next.js App Router or other RSC-enabled frameworks. The vulnerability is distinct from the earlier React2Shell (CVE-2025-55182) RCE but shares the same deserialization layer, and an incomplete initial patch led to a follow-up vulnerability, CVE-2025-67779, requiring further updates. Security advisories confirm that F5 products are not directly affected by CVE-2025-55184, but F5's WAF solutions can be used to mitigate the impact for organizations using vulnerable backend applications. Remediation steps include upgrading to the latest patched versions of React and Next.js, ensuring all related vulnerabilities are addressed, and rescanning for follow-up CVEs. Organizations are advised not to rely solely on early patches and to validate that all vulnerable RSC packages and serialization paths are fully remediated to prevent exploitation of this DoS flaw.
Mar 21, 2026