CWE-1258 Base Draft

Exposure of Sensitive System Information Due to Uncleared Debug Information

This vulnerability occurs when hardware fails to erase sensitive data like cryptographic keys and intermediate values before entering debug mode, leaving them exposed.

Definition

What is CWE-1258?

This vulnerability occurs when hardware fails to erase sensitive data like cryptographic keys and intermediate values before entering debug mode, leaving them exposed.
During normal operation, hardware components temporarily store security-critical data in registers or cache. This includes encryption keys, intermediate calculation results from cryptographic processes, and other sensitive system information. If this data isn't proactively wiped when the system switches into debug mode, it remains resident in memory. Attackers or untrusted users with debug access can then read these uncleared values directly, potentially compromising entire security systems. This exposure bypasses software protections because the leak happens at the hardware level, where sensitive artifacts were never properly sanitized during the mode transition.
Real-world impact

Real-world CVEs caused by CWE-1258

  • CVE-2021-33080

    Uncleared debug information in memory accelerator for SSD product exposes sensitive system information

  • CVE-2022-31162

    Rust library leaks Oauth client details in application debug logs

How attackers exploit it

Step-by-step attacker path

  1. 1

    A cryptographic core in a System-On-a-Chip (SoC) is used for cryptographic acceleration and implements several cryptographic operations (e.g., computation of AES encryption and decryption, SHA-256, HMAC, etc.). The keys for these operations or the intermediate values are stored in registers internal to the cryptographic core. These internal registers are in the Memory Mapped Input Output (MMIO) space and are blocked from access by software and other untrusted agents on the SoC. These registers are accessible through the debug and test interface.

  2. 2

    The following code example is extracted from the AES wrapper module, aes1_wrapper, of the Hack@DAC'21 buggy OpenPiton System-on-Chip (SoC). Within this wrapper module are four memory-mapped registers: core_key, core_key0, core_key1, and core_key2. Core_key0, core_key1, and core_key2 hold encryption/decryption keys. The core_key register selects a key and sends it to the underlying AES module to execute encryption/decryption operations. Debug mode in processors and SoCs facilitates design debugging by granting access to internal signal/register values, including physical pin values of peripherals/core, fabric bus data transactions, and inter-peripheral registers. Debug mode allows users to gather detailed, low-level information about the design to diagnose potential issues. While debug mode is beneficial for diagnosing processors or SoCs, it also introduces a new attack surface for potential attackers. For instance, if an attacker gains access to debug mode, they could potentially read any content transmitted through the fabric bus or access encryption/decryption keys stored in cryptographic peripherals. Therefore, it is crucial to clear the contents of secret registers upon entering debug mode. In the provided example of flawed code below, when debug_mode_i is activated, the register core_key0 is set to zero to prevent AES key leakage during debugging. However, this protective measure is not applied to the core_key1 register [REF-1435], leaving its contents uncleared during debug mode. This oversight enables a debugger to access sensitive information. Failing to clear sensitive data during debug mode may lead to unauthorized access to secret keys and compromise system security.

  3. 3

    To address the issue, it is essential to ensure that the register is cleared and zeroized after activating debug mode on the SoC. In the correct implementation illustrated in the good code below, core_keyx registers are set to zero when debug mode is activated [REF-1436].

Vulnerable code example

Vulnerable Other

A cryptographic core in a System-On-a-Chip (SoC) is used for cryptographic acceleration and implements several cryptographic operations (e.g., computation of AES encryption and decryption, SHA-256, HMAC, etc.). The keys for these operations or the intermediate values are stored in registers internal to the cryptographic core. These internal registers are in the Memory Mapped Input Output (MMIO) space and are blocked from access by software and other untrusted agents on the SoC. These registers are accessible through the debug and test interface.

Vulnerable Other 
In the above scenario, registers that store keys and intermediate values of cryptographic operations are not cleared when system enters debug mode. An untrusted actor running a debugger may read the contents of these registers and gain access to secret keys and other sensitive cryptographic information.
Secure code example

Secure Other

Secure Other 
Whenever the chip enters debug mode, all registers containing security-sensitive data are be cleared rendering them unreadable.
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist

How to prevent CWE-1258

  • Architecture and Design Whenever debug mode is enabled, all registers containing sensitive assets must be cleared.
Detection signals

How to detect CWE-1258

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-1258 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

Frequently asked questions

What is CWE-1258?

This vulnerability occurs when hardware fails to erase sensitive data like cryptographic keys and intermediate values before entering debug mode, leaving them exposed.

How serious is CWE-1258?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-1258?

MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Not Technology-Specific.

How can I prevent CWE-1258?

Whenever debug mode is enabled, all registers containing sensitive assets must be cleared.

How does Plexicus detect and fix CWE-1258?

Plexicus's SAST engine matches the data-flow signature for CWE-1258 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-1258?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1258.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-1258

CWE-212 Parent

Improper Removal of Sensitive Information Before Storage or Transfer

This vulnerability occurs when an application stores or transmits a resource containing sensitive data without properly cleaning it first,…

CWE-226 Sibling

Sensitive Information in Resource Not Removed Before Reuse

This vulnerability occurs when a system releases a resource like memory or a file for reuse but fails to erase the sensitive data it…

Resources

Further reading

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