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.)
CWE-565 Base Incomplete
Reliance on Cookies without Validation and Integrity Checking
This vulnerability occurs when an application uses cookies to make security decisions—like granting access or changing settings—but fails to verify that the cookie data is legitimate, unaltered, and…
Definition
What is CWE-565?
This vulnerability occurs when an application uses cookies to make security decisions—like granting access or changing settings—but fails to verify that the cookie data is legitimate, unaltered, and belongs to the current user.
Cookies are often used to store session identifiers, user preferences, or state information, but they are controlled by the client's browser. When an application blindly trusts cookie values without validating their integrity or checking if they match the authenticated user's session, attackers can forge or manipulate cookies to impersonate other users, escalate privileges, or bypass security controls.
To prevent this, developers should treat all client-side data, including cookies, as untrusted input. Implement server-side validation for any cookie used in security decisions, use cryptographically signed or encrypted cookies to prevent tampering, and bind session cookies to specific user attributes (like IP address or user agent) to detect session hijacking attempts.
Real-world impact
Real-world CVEs caused by CWE-565
-
e-dating application allows admin privileges by setting the admin cookie to 1.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable Java
The following code excerpt reads a value from a browser cookie to determine the role of the user.
Cookie[] cookies = request.getCookies();
for (int i =0; i< cookies.length; i++) {
Cookie c = cookies[i];
if (c.getName().equals("role")) {
userRole = c.getValue();
}
} 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-565
- Architecture and Design Avoid using cookie data for a security-related decision.
- Implementation Perform thorough input validation (i.e.: server side validation) on the cookie data if you're going to use it for a security related decision.
- Architecture and Design Add integrity checks to detect tampering.
- Architecture and Design Protect critical cookies from replay attacks, since cross-site scripting or other attacks may allow attackers to steal a strongly-encrypted cookie that also passes integrity checks. This mitigation applies to cookies that should only be valid during a single transaction or session. By enforcing timeouts, you may limit the scope of an attack. As part of your integrity check, use an unpredictable, server-side value that is not exposed to the client.
Detection signals
How to detect CWE-565
Plexicus auto-detects CWE-565 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-565?
How serious is CWE-565?
What languages or platforms are affected by CWE-565?
How can I prevent CWE-565?
How does Plexicus detect and fix CWE-565?
Where can I learn more about CWE-565?
Frequently asked questions
What is CWE-565?
This vulnerability occurs when an application uses cookies to make security decisions—like granting access or changing settings—but fails to verify that the cookie data is legitimate, unaltered, and belongs to the current user.
How serious is CWE-565?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-565?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-565?
Avoid using cookie data for a security-related decision. Perform thorough input validation (i.e.: server side validation) on the cookie data if you're going to use it for a security related decision.
How does Plexicus detect and fix CWE-565?
Plexicus's SAST engine matches the data-flow signature for CWE-565 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-565?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/565.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-565
CWE-642 Parent
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CWE-15 Sibling
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CWE-426 Sibling
Untrusted Search Path
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CWE-472 Sibling
External Control of Assumed-Immutable Web Parameter
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CWE-73 Sibling
External Control of File Name or Path
This vulnerability occurs when an application uses unvalidated user input to construct file or directory paths for filesystem operations.
CWE-784 Child
Reliance on Cookies without Validation and Integrity Checking in a Security Decision
This vulnerability occurs when an application makes security decisions—like granting access or verifying identity—based solely on cookie…
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