Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-385 Base Incomplete
Covert Timing Channel
A covert timing channel is a security flaw where an attacker can deduce secret information by observing how long certain operations take to execute. Instead of directly reading data, they analyze…
Definition
What is CWE-385?
A covert timing channel is a security flaw where an attacker can deduce secret information by observing how long certain operations take to execute. Instead of directly reading data, they analyze timing variations in system behavior to infer protected details.
Attackers can exploit timing differences to learn secrets they shouldn't have access to. For instance, if a cryptographic function or a database query takes slightly longer under specific conditions, that delay can leak information about the internal state of the operation or the data being processed. Monitoring these subtle time variations allows an attacker to piece together sensitive information.
This type of vulnerability is a classic example of a side-channel attack, specifically a timing channel. Common real-world signals include variations in a system's paging rate, the execution time of a transaction, or the delay in accessing a shared resource. Defending against these attacks requires ensuring that operations complete in constant time, regardless of the input or secret data involved.
Real-world impact
Real-world CVEs caused by CWE-385
No public CVE references are linked to this CWE in MITRE's catalog yet.
How attackers exploit it
Step-by-step attacker path
- 1
In this example, the attacker observes how long an authentication takes when the user types in the correct password.
- 2
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.
- 3
Note that in this example, the actual password must be handled in constant time as far as the attacker is concerned, even if the actual password is of an unusual length. This is one reason why it is good to use an algorithm that, among other things, stores a seeded cryptographic one-way hash of the password, then compare the hashes, which will always be of the same length.
Vulnerable code example
Vulnerable Python
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.
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 Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-385
- Architecture and Design Whenever possible, specify implementation strategies that do not introduce time variances in operations.
- Implementation Often one can artificially manipulate the time which operations take or -- when operations occur -- can remove information from the attacker.
- Implementation 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.
Detection signals
How to detect CWE-385
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
CWE-385
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Frequently asked questions What is CWE-385?
How serious is CWE-385?
What languages or platforms are affected by CWE-385?
How can I prevent CWE-385?
How does Plexicus detect and fix CWE-385?
Where can I learn more about CWE-385?
Frequently asked questions
What is CWE-385?
A covert timing channel is a security flaw where an attacker can deduce secret information by observing how long certain operations take to execute. Instead of directly reading data, they analyze timing variations in system behavior to infer protected details.
How serious is CWE-385?
MITRE rates the likelihood of exploit as Medium — exploitation is realistic but typically requires specific conditions.
What languages or platforms are affected by CWE-385?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-385?
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.
How does Plexicus detect and fix CWE-385?
Plexicus's SAST engine matches the data-flow signature for CWE-385 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-385?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/385.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-385
CWE-514 Parent
Covert Channel
A covert channel is a hidden communication path that allows data to be transmitted in a way that bypasses the system's intended security…
CWE-515 Sibling
Covert Storage Channel
A covert storage channel is a type of security flaw where one process secretly encodes data into a shared system resource (like a file,…
Resources
Further reading
- MITRE — official CWE-385 https://cwe.mitre.org/data/definitions/385.html
- The CLASP Application Security Process https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf
- A Taxonomy of Computer Program Security Flaws, with Examples https://cwe.mitre.org/documents/sources/ATaxonomyofComputerProgramSecurityFlawswithExamples%5BLandwehr93%5D.pdf
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