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Link to headingSummary
Two additional vulnerabilities in React Server Components have been identified: a high-severity Denial of Service (CVE-2025-55184) and a medium-severity Source Code Exposure (CVE-2025-55183). These issues were discovered while security researchers examined the patches for the original React2Shell vulnerability. The initial fix was incomplete and did not fully prevent denial-of-service attacks for all payload types, resulting in CVE-2025-67779.
Importantly, none of these new issues allow for Remote Code Execution.
We created new rules to address these vulnerabilities and deployed them to the Vercel WAF to automatically protect all projects hosted on Vercel at no cost. However, do not rely on the WAF for full protection. Immediate upgrades to a patched version are required.
Link to headingImpact
Link to headingDenial of Service (CVE-2025-55184)
A malicious HTTP request can be crafted and sent to any App Router endpoint that, when deserialized, can cause the server process to hang and consume CPU.
Link to headingSource Code Exposure (CVE-2025-55183)
A malicious HTTP request can be crafted and sent to any App Router endpoint that can return the compiled source code of Server Actions. This could reveal business logic, but would not expose secrets unless they were hardcoded directly into Server Action's code.
These vulnerabilities are present in versions 19.0.0, 19.0.1, 19.1.0, 19.1.1, 19.1.2, 19.2.0, and 19.2.1 of the following packages:
react-server-dom-parcelreact-server-dom-webpackreact-server-dom-turbopack
These packages are included in the following frameworks and bundlers:
Next.js:
13.x,14.x,15.x, and16.x.Other frameworks and plugins that embed or depend on React Server Components implementation (e.g., Vite, Parcel, React Router, RedwoodSDK, Waku)
Link to headingResolution
After creating mitigations to address these vulnerabilities, we deployed them across our globally-distributed platform to protect our customers. We still recommend upgrading to the latest patched version.
Updated releases of React and affected downstream frameworks include fixes to prevent these issues. All users should upgrade to a patched version as soon as possible.
Link to headingFixed in
React:
19.0.2,19.1.3,19.2.2.Next.js:
14.2.35,15.0.7,15.1.11,15.2.8,15.3.8,15.4.10,15.5.9,15.6.0-canary.60,16.0.10,16.1.0-canary.19.
Frameworks and bundlers using the aforementioned packages should install the latest versions provided by their respective maintainers.
Link to headingCredit
Thanks to RyotaK from GMO Flatt Security Inc. and Andrew MacPherson for identifying and responsibly reporting these vulnerabilities, and the Meta Security and React teams for their partnership.