A flaw was found in the util-linux chfn and chsh utilities when compiled with Readline support. The Readline library uses an INPUTRC environment variable to get a path to the library config file. When the library cannot parse the specified file, it prints an error message containing data from the file. This flaw allows an unprivileged user to read root-owned files, potentially leading to privilege escalation. This flaw affects util-linux versions prior to 2.37.4.
Weakness
The product generates an error message that includes sensitive information about its environment, users, or associated data.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Util-linux |
Kernel |
* |
2.37.4 (excluding) |
| Util-linux |
Ubuntu |
trusty |
* |
| Util-linux |
Ubuntu |
xenial |
* |
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.
References