React Server Components security update: DoS and Source Code Exposure
Two vulnerabilities in React Server Components have been patched: a high-severity Denial of Service attack (CVE-2025-55184) that can hang servers and a medium-severity Source Code Exposure issue (CVE-2025-55183) that can leak compiled source code. All users should upgrade to the latest patched versions of React, Next.js, and affected downstream frameworks immediately.
See the for the latest updates.Security Bulletin
Summary
Impact
Resolution
Fixed in
Credit
References
Two additional vulnerabilities in React Server Components have been identified: a high-severity Denial of Service () and a medium-severity Source Code Exposure (). 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-2025-55184CVE-2025-55183CVE-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.
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.
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 , , , , , , and of the following packages:19.0.019.0.119.1.019.1.119.1.219.2.019.2.1
These packages are included in the following frameworks and bundlers:
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.
Frameworks and bundlers using the aforementioned packages should install the latest versions provided by their respective maintainers.
Thanks to from GMO Flatt Security Inc. and for identifying and responsibly reporting these vulnerabilities, and the Meta Security and React teams for their partnership.RyotaKAndrew MacPherson
Denial of Service ()CVE-2025-55184
Source Code Exposure ()CVE-2025-55183
react-server-dom-parcelreact-server-dom-webpackreact-server-dom-turbopack
: , , , and .Next.js
13.x14.x15.x16.xOther frameworks and plugins that embed or depend on React Server Components implementation (e.g., Vite, Parcel, React Router, RedwoodSDK, Waku)
.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
Source: original entry ↗
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