CWE-14: Compiler Removal of Code to Clear Buffers | Glexia
CWE-14 (Compiler Removal of Code to Clear Buffers) weakness overview with consequences, detection methods, mitigations, related CVEs and MITRE ATT&CK context.
Glexia's Take · Automated analysis
CWE-14: Compiler Removal of Code to Clear Buffers
Compiler Removal of Code to Clear Buffers represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Confidentiality Access Control: Read Memory Bypass Protection Mechanism: This weakness will allow data that has not been cleared from memory to be read. If this data contains sensitive password information, then an attacker can read the password and use the information to bypass protection mechanisms.
Developer Pattern
CWE-14 is the kind of defect developers can usually prevent with explicit validation, safer framework defaults, and tests that exercise hostile input or unsafe state transitions.
Automation confidence
high confidence from CWE-14, 4.20.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Official CWE Definition
CWE-14: Compiler Removal of Code to Clear Buffers
Sensitive memory is cleared according to the source code, but compiler optimizations leave the memory untouched when it is not read from again, aka "dead store removal."
This compiler optimization error occurs when: Secret data are stored in memory. The secret data are scrubbed from memory by overwriting its contents. The source code is compiled using an optimizing compiler, which identifies and removes the function that overwrites the contents as a dead store because the memory is not used subsequently.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- The following code reads a password from the user, uses the password to connect to a back-end mainframe, and then attempts to scrub the password from memory using memset(). The code in the example will behave correctly if it is executed verbatim, but if the code is compiled using an optimizing compiler, then the call to memset() might be removed as a dead store, because the buffer pwd is not used after its value is overwritten. Because the buffer pwd contains a sensitive value, the application may be vulnerable to attack if the data are left memory resident. If attackers are able to access the correct region of memory, they may use the recovered password to gain control of the system. It is common practice to overwrite sensitive data manipulated in memory, such as passwords or cryptographic keys, in order to prevent attackers from learning system secrets. However, with the advent of optimizing compilers, programs do not always behave as their source code alone would suggest. In the example, the compiler interprets the call to memset() as dead code because the memory being written to is not subsequently used, despite the fact that there is clearly a security motivation for the operation to occur. The problem here is that many compilers, and in fact many programming languages, do not take this and other security concerns into consideration in their efforts to improve efficiency. Attackers typically exploit this type of vulnerability by using a core dump or runtime mechanism to access the memory used by a particular application and recover the secret information. Once an attacker has access to the secret information, it is relatively straightforward to further exploit the system and possibly compromise other resources with which the application interacts.
Remediation
- Implementation: Store the sensitive data in a "volatile" memory location if available.
- Build and Compilation: If possible, configure your compiler so that it does not remove dead stores.
- Architecture and Design: Where possible, encrypt sensitive data that are used by a software system.
Detection
- Black Box: This specific weakness is impossible to detect using black box methods. While an analyst could examine memory to see that it has not been scrubbed, an analysis of the executable would not be successful. This is because the compiler has already removed the relevant code. Only the source code shows whether the programmer intended to clear the memory or not, so this weakness is indistinguishable from others.
- White Box: This weakness is only detectable using white box methods (see black box detection factor). Careful analysis is required to determine if the code is likely to be removed by the compiler.
Mappings
Related CVEs, CWEs, and ATT&CK context
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.