CWE-1320: Improper Protection for Outbound Error Messages and Alert Signals

Description

Untrusted agents can disable alerts about signal conditions exceeding limits or the response mechanism that handles such alerts.

Hardware sensors are used to detect whether a device is operating within design limits. The threshold values for these limits are set by hardware fuses or trusted software such as a BIOS. Modification of these limits may be protected by hardware mechanisms. When device sensors detect out of bound conditions, alert signals may be generated for remedial action, which may take the form of device shutdown or throttling. Warning signals that are not properly secured may be disabled or used to generate spurious alerts, causing degraded performance or denial-of-service (DoS). These alerts may be masked by untrusted software. Examples of these alerts involve thermal and power sensor alerts.

Potential Impact

Availability

DoS: Instability, DoS: Crash, Exit, or Restart, Reduce Reliability, Unexpected State

Demonstrative Examples

Consider a platform design where a Digital-Thermal Sensor (DTS) is used to monitor temperature and compare that output against a threshold value.
							If the temperature output equals or exceeds the threshold value, the DTS unit sends an alert signal to the processor. 
						 The processor, upon getting the alert, input triggers system shutdown. The alert signal is handled as a General-Purpose-I/O (GPIO) pin in input mode.

Bad

The processor-GPIO controller exposes software-programmable controls that allow untrusted software to reprogram the state of the GPIO pin.

Reprogramming the state of the GPIO pin allows malicious software to trigger spurious alerts or to set the alert pin to a zero value so that thermal sensor alerts are not received by the processor.

Good

The GPIO alert-signal pin is blocked from untrusted software access and is controlled only by trusted software, such as the System BIOS.

Mitigations & Prevention

Architecture and Design

Alert signals generated by critical events should be protected from access by untrusted agents. Only hardware or trusted firmware modules should be able to alter the alert configuration.

Frequently Asked Questions

What is CWE-1320?

CWE-1320 (Improper Protection for Outbound Error Messages and Alert Signals) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. Untrusted agents can disable alerts about signal conditions exceeding limits or the response mechanism that handles such alerts.

How can CWE-1320 be exploited?

Attackers can exploit CWE-1320 (Improper Protection for Outbound Error Messages and Alert Signals) to dos: instability, dos: crash, exit, or restart, reduce reliability, unexpected state. This weakness is typically introduced during the Architecture and Design, Implementation phase of software development.

How do I prevent CWE-1320?

Key mitigations include: Alert signals generated by critical events should be protected from access by untrusted agents. Only hardware or trusted firmware modules should be able to alter the alert configuration.

What is the severity of CWE-1320?

CWE-1320 is classified as a Base-level weakness (Medium abstraction). Its actual severity depends on the specific context and how the weakness manifests in your application.