CVE-2026-49265

A flaw was found in oauthlib. A timing side-channel vulnerability in the Proof Key for Code Exchange (PKCE) validation process allows a remote attacker to recover secret verification codes. Because comparison operations do not execute in constant time, an attacker who has intercepted an authorization code can measure response latency differences across repeated requests to infer the expected verification code character-by-character. Successful exploitation allows the attacker to exchange the authorization code for an access token and impersonate the victim user.

This vulnerability is rated as having a Moderate impact because successful exploitation requires multiple stringent prerequisites, including intercepting a valid authorization code, measuring high-resolution network response times, and an OAuth server implementation that permits repeated verification attempts without revoking the code. While oauthlib facilitates PKCE validation in OAuth 2.0 deployments across Red Hat environments, the timing discrepancies are minor and highly susceptible to network noise in real-world scenarios. Consequently, extracting secret verifiers remotely presents significant practical hurdles.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.