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-293 Variant Draft
Using Referer Field for Authentication
This vulnerability occurs when a web application uses the HTTP Referer header as a sole or primary method for authentication or authorization decisions. Since this header is entirely controlled by…
Definition
What is CWE-293?
This vulnerability occurs when a web application uses the HTTP Referer header as a sole or primary method for authentication or authorization decisions. Since this header is entirely controlled by the user's browser or client and can be easily forged, it provides no reliable security.
The HTTP Referer header is designed to tell a server which page a user came from, but it was never intended for security. Treating it as a trusted credential is like using a 'recommended by a friend' note for building access—anyone can write it. Developers might implement this check to prevent cross-site request forgery (CSRF) or to restrict direct URL access, but because attackers can fully manipulate the header with simple tools like a proxy or browser extension, this defense is completely ineffective.
To properly secure authentication and authorization, always use established server-side mechanisms like session tokens, CSRF tokens, or standard authentication protocols (OAuth, SAML). These methods rely on secrets or cryptographic signatures that the client cannot easily forge. Relying on the Referer header creates a false sense of security and leaves critical application functions exposed to trivial bypass attacks.
Real-world impact
Real-world CVEs caused by CWE-293
No public CVE references are linked to this CWE in MITRE's catalog yet.
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 C++
The following code samples check a packet's referer in order to decide whether or not an inbound request is from a trusted host.
String trustedReferer = "http://www.example.com/"
while(true){
n = read(newsock, buffer, BUFSIZE);
requestPacket = processPacket(buffer, n);
if (requestPacket.referer == trustedReferer){
openNewSecureSession(requestPacket);
}
} 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-293
- Architecture and Design In order to usefully check if a given action is authorized, some means of strong authentication and method protection must be used. Use other means of authorization that cannot be simply spoofed. Possibilities include a username/password or certificate.
Detection signals
How to detect CWE-293
CWE-293
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Frequently asked questions What is CWE-293?
How serious is CWE-293?
What languages or platforms are affected by CWE-293?
How can I prevent CWE-293?
How does Plexicus detect and fix CWE-293?
Where can I learn more about CWE-293?
Frequently asked questions
What is CWE-293?
This vulnerability occurs when a web application uses the HTTP Referer header as a sole or primary method for authentication or authorization decisions. Since this header is entirely controlled by the user's browser or client and can be easily forged, it provides no reliable security.
How serious is CWE-293?
MITRE rates the likelihood of exploit as High — this weakness is actively exploited in the wild and should be prioritized for remediation.
What languages or platforms are affected by CWE-293?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-293?
In order to usefully check if a given action is authorized, some means of strong authentication and method protection must be used. Use other means of authorization that cannot be simply spoofed. Possibilities include a username/password or certificate.
How does Plexicus detect and fix CWE-293?
Plexicus's SAST engine matches the data-flow signature for CWE-293 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-293?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/293.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-293
CWE-290 Parent
Authentication Bypass by Spoofing
This weakness occurs when an application's authentication system can be tricked into accepting forged or manipulated credentials, allowing…
CWE-291 Sibling
Reliance on IP Address for Authentication
This vulnerability occurs when a system uses a client's IP address as the sole or primary method to verify their identity.
CWE-350 Sibling
Reliance on Reverse DNS Resolution for a Security-Critical Action
This vulnerability occurs when an application uses a reverse DNS lookup on an IP address to get a hostname and then uses that hostname for…
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