What is CWE-203?
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
Analyzing data...
CWE-203: Observable Discrepancy
Data statistics
RELATED CVES (365 DAYS)33
ABSTRACTIONBase
Vulnerabilities mapped to CWE-203
33 vulnerabilities560% increase year over year
Vulnerabilities in CISA KEV for CWE-203
0 vulnerabilities
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
Discrepancies may be observable based on timing, control flow, communications (such as replies or requests), or general behavior.
Characteristics
Alternate terms
- Side Channel Attack — Observable Discrepancies are at the root of side channel attacks.
Modes of introduction
- Architecture and Design
- Implementation
Common consequences
| Impact | Scope | Explanation |
|---|---|---|
| Read Application Data, Bypass Protection Mechanism | Confidentiality, Access Control | An attacker can gain access to sensitive information about the system, including authentication information that may allow an attacker to gain access to the system. Other security-relevant information about the operation or internal state of the product may be revealed to an unauthorized actor, such as whether a particular operation was successful or not. |
| Read Application Data | Confidentiality | In some cases, discrepancies can be used by attackers to form a side channel. When cryptographic primitives are vulnerable to side-channel attacks, this could be used to reveal unencrypted plaintext in the worst case. |
Risk mitigations
- Separation of Privilege · Architecture and DesignCompartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
- ImplementationEnsure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success. If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.
Representative vulnerabilities
Below are representative vulnerabilities related to this CWE, prioritized by severity.
Sources (2)
CWE™ Program, operated by The MITRE Corporation. Copyright © 2006–2026, The MITRE Corporation. The MITRE Corporation hereby grants you a non-exclusive, royalty-free license to use CWE for research, development, and commercial purposes. CWE Terms of Use.
Learn more
Run an in-depth assessment with complete web risk management
CyStack VulnScan continuously discovers assets, validates vulnerabilities, and helps security teams prioritize remediation across the organization.
Explore CyStack VulnScan
