CVE-2026-41213: Node-OAuth Node-oauth/oauth2-Server

Medium severity, CVSS 5.9. EPSS: 0.3% chance of exploitation in the next 30 days.

@node-oauth/oauth2-server is a module for implementing an OAuth2 server in Node.js. The token exchange path accepts RFC7636-invalid code_verifier values (including one-character strings) for S256 PKCE flows. Because short/weak verifiers are accepted and failed verifier attempts do not consume the authorization code, an attacker who intercepts an authorization code can brute-force code_verifier guesses online until token issuance succeeds.

Affected products

• Node-OAuth Node-oauth/oauth2-Server: before 5.3.0 (fixed in 5.3.0)

Published 2026-04-23. Last modified 2026-06-17.