# CVE-2026-126187: React: Unauthenticated Remote Code Execution in React Server Components - **Severity:** Critical 9.5 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:N`) - **Exploited in the wild:** Not known - **Fix available:** Yes - **Published:** 10 Nov 2026 - **Updated:** 10 Nov 2026 - **Also known as:** GHSA-xqc2-xf4c-x3h3, UBUNTU-CVE-2026-126187 ## What is CVE-2026-126187? CVE-2026-126187 is a critical vulnerability in react, published on 10 Nov 2026. ### Official description React is a JavaScript library for building user interfaces. From 19.0.0 until 19.0.9, 19.1.10, 19.2.9, and 19.3.1, the react-server-dom-webpack, react-server-dom-parcel, and react-server-dom-turbopack packages are vulnerable to unauthenticated remote code execution through crafted payloads targeting frameworks that support React Server Components. The vulnerability only affects extremely rare cases where responses transport multiple typed arrays and an attacker-controlled value. Applications whose React code does not use a server are not affected. Applications that do not use a framework, bundler, or bundler plugin that supports React Server Components are not affected. This issue is fixed in versions 19.0.9, 19.1.10, 19.2.9, and 19.3.1. Weakness: CWE-502 (Deserialization of Untrusted Data) ## Which versions are affected by CVE-2026-126187? 12 open source packages ship an affected version, including react-server-dom-parcel, react-server-dom-turbopack and react-server-dom-webpack. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `react-server-dom-parcel` | npm | From 19.0.0 | 19.0.9 | | `react-server-dom-parcel` | npm | From 19.1.0 | 19.1.10 | | `react-server-dom-parcel` | npm | From 19.2.0 | 19.2.9 | | `react-server-dom-parcel` | npm | From 19.3.0 | 19.3.1 | | `react-server-dom-turbopack` | npm | From 19.0.0 | 19.0.9 | | `react-server-dom-turbopack` | npm | From 19.1.0 | 19.1.10 | | `react-server-dom-turbopack` | npm | From 19.2.0 | 19.2.9 | | `react-server-dom-turbopack` | npm | From 19.3.0 | 19.3.1 | | `react-server-dom-webpack` | npm | From 19.0.0 | 19.0.9 | | `react-server-dom-webpack` | npm | From 19.1.0 | 19.1.10 | | `react-server-dom-webpack` | npm | From 19.2.0 | 19.2.9 | | `react-server-dom-webpack` | npm | From 19.3.0 | 19.3.1 | ## How do I fix CVE-2026-126187? Upgrade react-server-dom-parcel to a fixed version for your release line: 19.0.9, 19.1.10, 19.2.9 or 19.3.1. ## Is CVE-2026-126187 being exploited? There is no known exploitation of CVE-2026-126187 in the wild and no public exploit code. Public exploit code: - CVE-2026-126187 Unauthenticated RCE in React Server Components - PoC and Docker lab for GHSA-xqc2-xf4c-x3h3 / GHSA-673q-mjm6-r5xr (github_poc): https://github.com/briskets/CVE-2026-126187-poc - PoC: unauth RCE via Next.js use-cache typed-array framing desync (CVE-2026-126187 / GHSA-xqc2-xf4c-x3h3) | docker compose lab (github_poc): https://github.com/TahuCryptsi/poc-cve-2026-126187-rsc-usecache-rce - Dockerized remote RCE PoC for GHSA-673q-mjm6-r5xr (Next.js use cache / React Flight, CVE-2026-126187): one unauthenticated request -> code execution, with a patched victim that is immune. (github_poc): https://github.com/rudSarkar/GHSA-673q-mjm6-r5xr ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-126187 and fix it if it is affected. What it is: CVE-2026-126187 is a critical vulnerability in react, published on 10 Nov 2026. Exploitation: There is no known exploitation of CVE-2026-126187 in the wild and no public exploit code. Affected packages and fixed versions: - react-server-dom-parcel (npm): affected from 19.0.0; fixed in 19.0.9 - react-server-dom-parcel (npm): affected from 19.1.0; fixed in 19.1.10 - react-server-dom-parcel (npm): affected from 19.2.0; fixed in 19.2.9 - react-server-dom-parcel (npm): affected from 19.3.0; fixed in 19.3.1 - react-server-dom-turbopack (npm): affected from 19.0.0; fixed in 19.0.9 - react-server-dom-turbopack (npm): affected from 19.1.0; fixed in 19.1.10 - react-server-dom-turbopack (npm): affected from 19.2.0; fixed in 19.2.9 - react-server-dom-turbopack (npm): affected from 19.3.0; fixed in 19.3.1 - react-server-dom-webpack (npm): affected from 19.0.0; fixed in 19.0.9 - react-server-dom-webpack (npm): affected from 19.1.0; fixed in 19.1.10 - react-server-dom-webpack (npm): affected from 19.2.0; fixed in 19.2.9 - react-server-dom-webpack (npm): affected from 19.3.0; fixed in 19.3.1 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-126187/ (Markdown: https://insights.sbomify.com/CVE-2026-126187/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126187 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126187 - OSV: https://osv.dev/vulnerability/CVE-2026-126187 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-126187/ Summaries are generated and may contain mistakes; the official description above is the record.