CVE-2026-42565 is a medium-severity (CVSS 4.3) Open Redirect vulnerability in @workos/authkit-session. A fix is available for @workos/authkit-session — see the affected versions and patch details below.
@workos/authkit-session: Open Redirect via state-derived redirect target
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
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@workos/authkit-sessionnpmDescription
An open redirect vulnerability exists in AuthService.handleCallback due to insufficient validation of the returnPathname value derived from the OAuth state parameter.
The state parameter is round-tripped through the identity provider (IdP) and can be influenced by an attacker. The handleCallback function decodes and returns returnPathname without enforcing restrictions on origin or scheme. As a result, attacker-controlled values (e.g., https://evil.com/, //evil.com, or similar variants) may be returned to the application.
If this value is used directly in a redirect (e.g., via an HTTP Location header, framework redirect helpers, or client-side navigation), it may cause the user to be redirected to an external, attacker-controlled site.
Security Impact This issue may be used to facilitate phishing or user redirection attacks by leveraging the trust of the originating domain. For example, an attacker could craft a link that directs a user through a legitimate authentication flow and then redirects them to an external site.
The severity depends on how returnPathname is used by the application. Exploitation requires:
- The application to use
returnPathnameas a redirect target, and - The absence of downstream validation or allowlisting
This vulnerability does not enable authentication bypass, token disclosure, or direct account compromise on its own, but may increase the effectiveness of social engineering attacks when combined with user interaction.
Vulnerability Type CWE-601: URL Redirection to Untrusted Site (Open Redirect)
Patches Patched in https://github.com/workos/authkit-session/releases/tag/v0.5.1
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @workos/authkit-session | all versions | 0.5.1npm install @workos/authkit-session@0.5.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @workos/authkit-session, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @workos/authkit-session to 0.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42565 is resolved across your whole dependency graph.
Workarounds
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-2026-42565 in your dependencies?
Find it across npm, including transitive dependencies.