CWE-479: Signal Handler Use of a Non-reentrant Function | Glexia
CWE-479 (Signal Handler Use of a Non-reentrant Function) weakness overview with consequences, detection methods, mitigations, related CVEs and MITRE ATT&CK context.
Glexia's Take · Automated analysis
CWE-479: Signal Handler Use of a Non-reentrant Function
Signal Handler Use of a Non-reentrant Function represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- Integrity Confidentiality Availability: Execute Unauthorized Code or Commands: It may be possible to execute arbitrary code through the use of a write-what-where condition.
- Integrity: Modify Memory Modify Application Data: Signal race conditions often result in data corruption.
Developer Pattern
CWE-479 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-479, 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-479: Signal Handler Use of a Non-reentrant Function
The product defines a signal handler that calls a non-reentrant function.
Non-reentrant functions are functions that cannot safely be called, interrupted, and then recalled before the first call has finished without resulting in memory corruption. This can lead to an unexpected system state and unpredictable results with a variety of potential consequences depending on context, including denial of service and code execution. Many functions are not reentrant, but some of them can result in the corruption of memory if they are used in a signal handler. The function call syslog() is an example of this. In order to perform its functionality, it allocates a small amount of memory as "scratch space." If syslog() is suspended by a signal call and the signal handler calls syslog(), the memory used by both of these functions enters an undefined, and possibly, exploitable state. Implementations of malloc() and free() manage metadata in global structures in order to track which memory is allocated versus which memory is available, but they are non-reentrant. Simultaneous calls to these functions can cause corruption of the metadata.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- In this example, a signal handler uses syslog() to log a message:
Remediation
- Requirements: Require languages or libraries that provide reentrant functionality, or otherwise make it easier to avoid this weakness.
- Architecture and Design: Design signal handlers to only set flags rather than perform complex functionality.
- Implementation: Ensure that non-reentrant functions are not found in signal handlers.
- Implementation: Use sanity checks to reduce the timing window for exploitation of race conditions. This is only a partial solution, since many attacks might fail, but other attacks still might work within the narrower window, even accidentally.
Detection
- Automated Static Analysis: Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Mappings
Related CVEs, CWEs, and ATT&CK context
Related CWEs
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.