AI description
CVE-2025-66456 refers to a critical remote code execution (RCE) vulnerability found in React Server Components (RSC), specifically within the Flight protocol. This vulnerability, initially tracked under CVE-2025-55182 (React) and CVE-2025-66478 (Next.js) (CVE-2025-66478 was later rejected as a duplicate of CVE-2025-55182), allows unauthenticated attackers to execute arbitrary code on the server. The flaw stems from insecure deserialization of malicious HTTP requests sent to React Server Function endpoints. Successful exploitation of CVE-2025-66456 enables attackers to influence server-side execution logic, leading to the execution of privileged JavaScript code on the server. It was reported that the exploit has near-100% reliability and requires no code changes to be effective against default configurations. A fix was introduced in React versions 19.0.1, 19.1.2, and 19.2.1.
- Description
- Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.0 through 1.4.16 contain a prototype pollution vulnerability in `mergeDeep` after merging results of two standard schema validations with the same key. Due to the ordering of merging, there must be an any type that is set as a standalone guard, to allow for the `__proto__ prop` to be merged. When combined with GHSA-8vch-m3f4-q8jf this allows for a full RCE by an attacker. This issue is fixed in version 1.4.17. To workaround, remove the `__proto__ key` from body.
- Source
- security-advisories@github.com
- NVD status
- Received
CVSS 4.0
- Type
- Secondary
- Base score
- 9.1
- Impact score
- -
- Exploitability score
- -
- Vector string
- CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- Severity
- CRITICAL
- security-advisories@github.com
- CWE-1321
Hype score is a measure of social media activity compared against trending CVEs from the past 12 months. Max score 100.
- Hype score
26
CVE-2025-66456 Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.0 through 1.4.16 contain … https://t.co/z2yJde4wPk
@CVEnew
10 Dec 2025
137 Impressions
0 Retweets
0 Likes
0 Bookmarks
0 Replies
0 Quotes
CVE-2025-66456 | Critical 9.1/10 Prototype Pollution affecting routes with Standard Schema with multiple Standalone Schemas We highly recommend updating Elysia to 1.4.17 or higher immediately https://t.co/ZohocHIcW7
@saltyAom
9 Dec 2025
27799 Impressions
19 Retweets
359 Likes
57 Bookmarks
12 Replies
5 Quotes