CVE-2019-7644

Auth0 Auth0-WCF-Service-JWT before 1.0.4 leaks the expected JWT signature in an error message when it cannot successfully validate the JWT signature. If this error message is presented to an attacker, they can forge an arbitrary JWT token that will be accepted by the vulnerable application.

Weakness

The product generates an error message that includes sensitive information about its environment, users, or associated data.

Affected Software

Extended Description

The sensitive information may be valuable information on its own (such as a password), or it may be useful for launching other, more serious attacks. The error message may be created in different ways:

An attacker may use the contents of error messages to help launch another, more focused attack. For example, an attempt to exploit a path traversal weakness (CWE-22) might yield the full pathname of the installed application. In turn, this could be used to select the proper number of “..” sequences to navigate to the targeted file. An attack using SQL injection (CWE-89) might not initially succeed, but an error message could reveal the malformed query, which would expose query logic and possibly even passwords or other sensitive information used within the query.

Potential Mitigations

• Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success.
• If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files.
• Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/215.html
• https://cwe.mitre.org/data/definitions/463.html
• https://cwe.mitre.org/data/definitions/54.html
• https://cwe.mitre.org/data/definitions/7.html

References

• https://auth0.com/docs/security/bulletins/cve-2019-7644