CVE-2026-11832

Vulnerability

The Dancer2::Plugin::Auth::OAuth module for Perl versions before 0.22 generates the OAuth 1.0 nonce using an MD5 hash of the current epoch time. According to RFC 5849 [1][2], nonces must be unique and unpredictable to prevent replay attacks. The use of a predictable value (epoch time) violates this requirement, making the nonce guessable by an attacker who can estimate the server's clock.

Exploitation

An attacker with knowledge of the approximate server time (e.g., via HTTP Date headers or NTP) can compute the same MD5 hash and predict the nonce value. The attacker does not need authentication but must be able to intercept or observe a legitimate OAuth request to capture the timestamp and then craft a replay request with the predicted nonce. No user interaction is required beyond the victim initiating an OAuth flow.

Impact

Successful exploitation allows an attacker to replay a captured OAuth request, potentially gaining unauthorized access to protected resources on behalf of the victim. The impact depends on the scope of the OAuth token; it could lead to information disclosure, data modification, or privilege escalation. The attack undermines the security guarantees of OAuth 1.0.

Mitigation

Upgrade to version 0.22 or later, which replaces the predictable nonce generation with a cryptographically secure random value. The fix was released on an unknown date; the changelog [3] documents the change. No workaround is available for earlier versions; users must update the module.