react-router: Inconsistent Interpretation of HTTP Requests
CVE-2025-31137 is a high-severity inconsistent interpretation of HTTP requests vulnerability in react-router from Remix-run, with a CVSS 3.0 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected react-router versions: >= 7.0.0, < 7.4.1; >= 2.11.1, < 2.16.3. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.2% chance of exploitation within 30 days, higher than 69% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of react-router you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Remix-run | react-router | >= 7.0.0, < 7.4.1; >= 2.11.1, < 2.16.3 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (github.com).
Official description
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 vulnerability allows anyone to spoof the URL used in an incoming Request by putting a URL pathname in the port section of a URL that is part of a Host or X-Forwarded-Host header sent to a Remix/React Router request handler. This issue has been patched and released in Remix 2.16.3 and React Router 7.4.1.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Inconsistent Interpretation of HTTP Requests
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
How developers prevent this class of flaw
- Use a web server that employs a strict HTTP parsing procedure, such as Apache.
- Terminate the client session after each request.
More Inconsistent Interpretation of HTTP Requests vulnerabilities (CWE-444)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in react-router
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 7.5 High severity
- 8.2 High severity
- 9.1 Critical severity
Recent Inconsistent Interpretation of HTTP Requests vulnerabilities
- 7.5 High severity
- 9.8 Critical severity
- 10.0 Critical severity
- 7.1 High severity
- 7.4 High severity
- 7.5 High severity
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