CVE-2025-62379 is a low-severity (CVSS 3.1) Open Redirect vulnerability in reflex. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.
Open Redirect in reflex-dev/reflex
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-62379.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
reflexReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Mitigation
Make sure GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN is not set in a production environment. So the following is correct:
assert os.getenv("GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN") is None
Vulnerability Description
Vulnerability Overview
- When the GET /auth-codespace page loads in a GitHub Codespaces environment, it automatically assigns the redirect_to query parameter value directly to client-side links without any validation and triggers automatic clicks. This allows attackers to redirect users to arbitrary external URLs.
- The route is only registered when a Codespaces environment is detected, and the detection is controlled by environment variables. This means that the same behavior can be activated in production if the corresponding environment variable is set.
Vulnerable Code Analysis
- This code assigns the redirect_to query parameter directly to a.href without any validation and immediately triggers a click (automatic navigation), allowing users to be sent to arbitrary external domains, resulting in an open redirect vulnerability.
- The execution condition is simply based on the presence of a sessionStorage flag, meaning it triggers immediately on first visits or in incognito/private browsing windows, with no server-side origin/scheme whitelist or internal path enforcement defenses in place.
PoC
PoC Description
<img width="623" height="497" alt="image" src="https://github.com/user-attachments/assets/55ef4828-09fa-451b-a7cc-8fcaad6a2a21" />- Used the production configuration from docker-example (docker-example/production-compose).
- Added a Codespaces detection environment variable to the app container in compose.yaml to forcibly expose the route.
- GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN: dummy
- The reverse proxy (Caddy) needs to be configured to forward /auth-codespace to the backend (required depending on the environment).
curl Example
https://localhost/auth-codespace?redirect_to=http://google.com
Impact
Phishing/Social Engineering Attacks
Users can be exploited by immediately redirecting from a trusted domain to external malicious sites, taking advantage of user trust. This enables login page spoofing, credential harvesting, and redirection to malware distribution pages.
Authentication/Session Flow Disruption
When users with valid sessions/cookies from the same origin click the link, they are redirected to unintended external domains, which can bypass or disrupt authentication/authorization flows. When combined with redirect-based flows like OAuth/OIDC, this can escalate into security incidents.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | reflex | ≥ 0.5.4 | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for reflex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of reflex for CVE-2025-62379. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.
Frequently Asked Questions
Is CVE-2025-62379 in your dependencies?
Find it across PyPI, including transitive dependencies.