CWE-585

Variant Abstraction Level
Pillar — Highest-level weakness category
Class — Abstract, language-independent
Base — Specific enough to detect
Variant — Tied to specific technology
Compound — Requires multiple weaknesses Draft MITRE CWE Status
Stable — Fully reviewed and complete
Draft — Under development, may change
Incomplete — Partially defined by MITRE
Deprecated — No longer recommended
Obsolete — Replaced by another CWE
Empty Synchronized Block

Description

The product contains an empty synchronized block.

An empty synchronized block does not actually accomplish any synchronization and may indicate a troubled section of code. An empty synchronized block can occur because code no longer needed within the synchronized block is commented out without removing the synchronized block.

Consequences

Other — Other

An empty synchronized block will wait until nobody else is using the synchronizer being specified. While this may be part of the desired behavior, because you haven't protected the subsequent code by placing it inside the synchronized block, nothing is stopping somebody else from modifying whatever it was you were waiting for while you run the subsequent code.

Mitigations

Phase: Implementation

When you come across an empty synchronized statement, or a synchronized statement in which the code has been commented out, try to determine what the original intentions were and whether or not the synchronized block is still necessary.

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.)