Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-309 Base Draft
Use of Password System for Primary Authentication
This weakness occurs when an application relies solely on password-based authentication as its main security gate. This single-factor approach is inherently vulnerable to a range of attacks that can…
Definition
What is CWE-309?
This weakness occurs when an application relies solely on password-based authentication as its main security gate. This single-factor approach is inherently vulnerable to a range of attacks that can compromise user accounts.
Relying only on passwords for authentication creates a single point of failure in your security model. Passwords are frequently weak, reused across sites, or stolen through phishing, data breaches, or brute-force attacks. Without additional safeguards, an attacker who obtains a password gains full access to the associated account and its privileges.
To mitigate this, you should implement defense-in-depth by adding secondary authentication factors (multi-factor authentication). Additionally, enforce strong password policies, use secure hashing algorithms (like Argon2 or bcrypt) for storage, and implement account lockouts or rate-limiting to thwart automated attacks. Treating passwords as the sole authentication method is a high-risk design choice in modern applications.
Real-world impact
Real-world CVEs caused by CWE-309
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
In both of these examples, a user is logged in if their given password matches a stored password:
unsigned char *check_passwd(char *plaintext) {
ctext = simple_digest("sha1",plaintext,strlen(plaintext), ... );
```
//Login if hash matches stored hash*
if (equal(ctext, secret_password())) {
```
login_user();
}
} 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-309
- Architecture and Design In order to protect password systems from compromise, the following should be noted: - Passwords should be stored safely to prevent insider attack and to ensure that -- if a system is compromised -- the passwords are not retrievable. Due to password reuse, this information may be useful in the compromise of other systems these users work with. In order to protect these passwords, they should be stored encrypted, in a non-reversible state, such that the original text password cannot be extracted from the stored value. - Password aging should be strictly enforced to ensure that passwords do not remain unchanged for long periods of time. The longer a password remains in use, the higher the probability that it has been compromised. For this reason, passwords should require refreshing periodically, and users should be informed of the risk of passwords which remain in use for too long. - Password strength should be enforced intelligently. Rather than restrict passwords to specific content, or specific length, users should be encouraged to use upper and lower case letters, numbers, and symbols in their passwords. The system should also ensure that no passwords are derived from dictionary words.
- Architecture and Design Use a zero-knowledge password protocol, such as SRP.
- Architecture and Design Ensure that passwords are stored safely and are not reversible.
- Architecture and Design Implement password aging functionality that requires passwords be changed after a certain point.
- Architecture and Design Use a mechanism for determining the strength of a password and notify the user of weak password use.
- Architecture and Design Inform the user of why password protections are in place, how they work to protect data integrity, and why it is important to heed their warnings.
Detection signals
How to detect CWE-309
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.
Plexicus auto-detects CWE-309 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-309?
How serious is CWE-309?
What languages or platforms are affected by CWE-309?
How can I prevent CWE-309?
How does Plexicus detect and fix CWE-309?
Where can I learn more about CWE-309?
Frequently asked questions
What is CWE-309?
This weakness occurs when an application relies solely on password-based authentication as its main security gate. This single-factor approach is inherently vulnerable to a range of attacks that can compromise user accounts.
How serious is CWE-309?
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-309?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-309?
In order to protect password systems from compromise, the following should be noted: - Passwords should be stored safely to prevent insider attack and to ensure that -- if a system is compromised -- the passwords are not retrievable. Due to password reuse, this information may be useful in the compromise of other systems these users work with. In order to protect these passwords, they should be stored encrypted, in a non-reversible state, such that the original text password cannot be…
How does Plexicus detect and fix CWE-309?
Plexicus's SAST engine matches the data-flow signature for CWE-309 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-309?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/309.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-309
CWE-1390 Parent
Weak Authentication
This vulnerability occurs when a system's login or identity verification process is too easy to bypass or fool. While it attempts to check…
CWE-1391 Sibling
Use of Weak Credentials
This vulnerability occurs when a system relies on weak authentication credentials—like default passwords, hard-coded keys, or easily…
CWE-262 Sibling
Not Using Password Aging
This vulnerability occurs when a system lacks password expiration policies, allowing users to keep the same password indefinitely.
CWE-263 Sibling
Password Aging with Long Expiration
The system enforces password changes, but the time allowed between changes is excessively long, weakening security.
CWE-289 Sibling
Authentication Bypass by Alternate Name
This vulnerability occurs when a system checks access based on a resource or user name, but fails to account for all the different names…
CWE-290 Sibling
Authentication Bypass by Spoofing
This weakness occurs when an application's authentication system can be tricked into accepting forged or manipulated credentials, allowing…
CWE-294 Sibling
Authentication Bypass by Capture-replay
This vulnerability occurs when an attacker can intercept and record legitimate authentication traffic, then replay it later to gain…
CWE-301 Sibling
Reflection Attack in an Authentication Protocol
A reflection attack is a flaw in mutual authentication protocols that allows an attacker to impersonate a legitimate user without knowing…
CWE-302 Sibling
Authentication Bypass by Assumed-Immutable Data
This vulnerability occurs when an authentication system incorrectly treats certain data as unchangeable, when in fact an attacker can…
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