Deserialization of Untrusted Data in React Router - CVE-2026-42211
Published: June 19, 2026
Vulnerability identifier: #VU134926
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-42211
CWE-ID: CWE-502
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Remix
Affected software:
React Router
React Router
Detailed vulnerability description
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to deserialization of untrusted data in React Router framework mode when handling external requests in an application that also contains an existing prototype pollution vulnerability. A remote attacker can send crafted external requests to execute arbitrary code.
Exploitation requires chaining with a pre-existing prototype pollution vulnerability in the application code and affects framework mode only.
How to mitigate CVE-2026-42211
Install security update from vendor's website.