CWE-385: Covert Timing Channel

Extended Description

In some instances, knowing when data is transmitted between parties can provide a malicious user with privileged information. Also, externally monitoring the timing of operations can potentially reveal sensitive data. For example, a cryptographic operation can expose its internal state if the time it takes to perform the operation varies, based on the state. Covert channels are frequently classified as either storage or timing channels. Some examples of covert timing channels are the system's paging rate, the time a certain transaction requires to execute, and the time it takes to gain access to a shared bus.

Code Examples & CVEs

Demonstrative Examples

In this example, the attacker observes how long an authentication takes when the user types in the correct password.

When the attacker tries their own values, they can first try strings of various length. When they find a string of the right length, the computation will take a bit longer, because the for loop will run at least once. Additionally, with this code, the attacker can possibly learn one character of the password at a time, because when they guess the first character right, the computation will take longer than a wrong guesses. Such an attack can break even the most sophisticated password with a few hundred guesses.

BadPython

def validate_password(actual_pw, typed_pw): 		                     if len(actual_pw) <> len(typed_pw): 		   return 0                    for i in len(actual_pw): 		   if actual_pw[i] <> typed_pw[i]: 		   return 0                                        return 1

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-385 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-385, Covert Timing Channel, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Covert Timing Channel during Architecture and Design

MITRE associates mitigation with Architecture and Design, and Implementation; recorded impacts include Read Application Data, and Other; the entry maps to CAPEC-462. Use these source-defined anchors to turn CWE-385 into implementation, review, and verification checks for the affected component.

CWE-385: Covert Timing Channel — MITRE CWE

Triage CWE-385 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-385, Covert Timing Channel, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-385

Apply MITRE's full root-cause mapping guidance when using CWE-385, Covert Timing Channel. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-385 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-385, Covert Timing Channel. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-385: Covert Timing Channel?+

CWE-385: Covert Timing Channel is a Common Weakness Enumeration (CWE) entry maintained by MITRE. Covert timing channels convey information by modulating some aspect of system behavior over time, so that the program receiving the information can observe system behavior and infer protected information. In some instances, knowing when data is transmitted between parties can provide a malicious user with privileged information. Also, externally monitoring the timing of operations can potentially reveal sensitive data. For example, a cryptographic operation can expose its internal state if the time it takes to perform the operation varies, based on the state. Covert channels are frequently classified as either storage or timing channels. Some examples of covert timing channels are the system's paging rate, the time a certain transaction requires to execute, and the time it takes to gain access to a shared bus.

What are the security consequences of Covert Timing Channel?+

If exploited, CWE-385 (Covert Timing Channel) it can compromise Confidentiality and Other, leading to outcomes such as Read Application Data and Other.

How do you prevent or mitigate Covert Timing Channel?+

Recommended mitigations for CWE-385 include: Whenever possible, specify implementation strategies that do not introduce time variances in operations. Often one can artificially manipulate the time which operations take or -- when operations occur -- can remove information from the attacker. It is reasonable to add artificial or random delays so that the amount of CPU time consumed is independent of the action being taken by the application.

Which programming languages are affected by Covert Timing Channel?+

CWE-385 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-385 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-385: Covert Timing Channel

Extended Description

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Phase

Description

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Description

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Description

Detection Methods

Code Examples & CVEs

Demonstrative Examples

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-385 with SSDF evidence

Address Covert Timing Channel during Architecture and Design

Triage CWE-385 against known exploitation evidence

Apply precise root-cause mapping to CWE-385

Validate CWE-385 with root-cause mapping checks

Frequently Asked Questions

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