Vulnerability in Remix-run React-router

CVE-2025-31137

React Router is a multi-strategy router for React bridging the gap from React 18 to React 19. There is a vulnerability in Remix/React Router that affects all Remix 2 and React Router 7 consumers using the Express adapter. Basically, this v…

Vulnerability class: HTTP Request Smuggling

EPSS: 0.001 (26.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2025-31137?
CVE-2025-31137 is a high-severity vulnerability in Remix-run React-router, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 7.5/10. Published 2025-04-01.
How severe is CVE-2025-31137?
High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2025-31137 known to be exploited?
3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.