CWE-690: Unchecked Return Value to NULL Pointer Dereference
Official CWE-690 CWE context with Glexia analysis, remediation guidance, related CVEs, and ATT&CK context.
Glexia's Take
CWE-690: Unchecked Return Value to NULL Pointer Dereference
Unchecked Return Value to NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Availability: DoS: Crash, Exit, or Restart
- Integrity,Confidentiality,Availability: Execute Unauthorized Code or Commands,Read Memory,Modify Memory: In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
Developer Pattern
CWE-690 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.
Confidence
high confidence from CWE-690, 4.20.
Official CWE Definition
CWE-690: Unchecked Return Value to NULL Pointer Dereference
The product does not check for an error after calling a function that can return with a NULL pointer if the function fails, which leads to a resultant NULL pointer dereference.
While unchecked return value weaknesses are not limited to returns of NULL pointers (see the examples in CWE-252), functions often return NULL to indicate an error status. When this error condition is not checked, a NULL pointer dereference can occur.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- The code below makes a call to the getUserName() function but doesn't check the return value before dereferencing (which may cause a NullPointerException).
- This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer. If an attacker provides an address that appears to be well-formed, but the address does not resolve to a hostname, then the call to gethostbyaddr() will return NULL. Since the code does not check the return value from gethostbyaddr (CWE-252), a NULL pointer dereference (CWE-476) would then occur in the call to strcpy().,Note that this code is also vulnerable to a buffer overflow (CWE-119).
Remediation
- Use safe APIs
- Centralize the control
- Add regression tests
- Review logs and telemetry for attempted abuse
Detection
- Black Box: This typically occurs in rarely-triggered error conditions, reducing the chances of detection during black box testing.
- White Box: Code analysis can require knowledge of API behaviors for library functions that might return NULL, reducing the chances of detection when unknown libraries are used.
- Automated Dynamic Analysis: Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].
Mappings
Related CVEs, CWEs, and ATT&CK context
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.