In x86s APIC (Advanced Programmable Interrupt Controller) architecture,
error conditions are reported in a status register. Furthermore, the OS
can opt to receive an interrupt when a new error occurs.
It is possible to configure the error interrupt with an illegal vector,
which generates an error when an error interrupt is raised.
This case causes Xen to recurse through vlapic_error(). The recursion
itself is bounded; errors accumulate in the the status register and only
generate an interrupt when a new status bit becomes set.
However, the lock protecting this state in Xen will try to be taken
recursively, and deadlock.
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 |
| Xen |
Ubuntu |
focal |
* |
| Xen |
Ubuntu |
oracular |
* |
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