File Session Storage Vulnerabilities in React Router and Remix Products
CVE-2025-61686

9.1CRITICAL

Key Information:

Vendor

Remix-run

Status
React-router
Vendor
CVE Published:
10 January 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2025-61686?

A vulnerability in the file session storage mechanism of React Router and Remix allows potential attackers to manipulate session data if an unsigned cookie is utilized with createFileSessionStorage(). This could lead to unauthorized attempts to read or write session data from locations outside the designated session file directory. While direct file access by attackers isn't possible, the exploit's success hinges on the web server process's permissions. Should the manipulated files align with the expected session file format, there's a risk that session information could inadvertently be revealed to the application, depending on its logic. This issue has been addressed in recent updates released by the vendor.

Affected Version(s)

react-router @react-router/node >= 7.0.0, < 7.9.4 < @react-router/node 7.0.0, 7.9.4

react-router @remix-run/deno < 2.17.2 < @remix-run/deno 2.17.2

react-router @remix-run/node < 2.17.2 < @remix-run/node 2.17.2

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2025-61686_docker
Created by FlowerWitch

References

https://github.com/remix-run/react-router/security/adviso...
x_refsource_CONFIRM

CVSS V3.1

Score:
9.1
Severity:
CRITICAL
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

JSON
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