Non-constant-time comparison of CSRF tokens in UIDL request handler in com.vaadin:vaadin-server versions 7.0.0 through 7.7.23 (Vaadin 7.0.0 through 7.7.23), and 8.0.0 through 8.12.2 (Vaadin 8.0.0 through 8.12.2) allows attacker to guess a security token via timing attack.
Vaadin applications use different types of tokens for different purposes, such as preventing CSRF, managing Push and Upload requests. The token checking implementation was subject to the theoretical possibility of timing attacks based on how long it takes for a request with invalid token to be rejected.
These timing attacks could result in exposure of the user's token, which can be used to blindly submit data on the user's behalf, without the possibility of reading back the responses, or of opening websockets and listening for published data from the server for that user, which may or may not contain sensitive information due to the application’s nature.
The vulnerability is fixed using constant-time comparison for all security tokens to prevent these potential timing attacks. Applications using the affected Vaadin versions should all be updated to the latest maintenance release.
Affected products and mitigation
Users of affected versions should apply the following mitigation or upgrade. Releases that have fixed this issue include: