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-304 Base Draft
Missing Critical Step in Authentication
This vulnerability occurs when a software authentication process omits a required step, weakening its overall security.
Definition
What is CWE-304?
This vulnerability occurs when a software authentication process omits a required step, weakening its overall security.
Secure authentication relies on following a defined protocol completely. Skipping a step—like not validating a session token, omitting a required cryptographic hash, or failing to check a second factor—creates a gap that attackers can exploit to bypass login protections or launch more effective brute-force attacks.
To prevent this, developers must treat authentication algorithms as strict checklists. Each step, from credential presentation to final session establishment, must be implemented and tested. Relying on official libraries and comprehensive security testing helps ensure no critical step is accidentally missing or disabled.
Real-world impact
Real-world CVEs caused by CWE-304
-
Shared secret not verified in a RADIUS response packet, allowing authentication bypass by spoofing server replies.
-
Chain: Authentication bypass by skipping the first startup step as required by the protocol.
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 pseudo
MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} 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-304
- Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
- Implementation Validate input at trust boundaries; use allowlists, not denylists.
- Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
- Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
- Operation Monitor logs for the runtime signals listed in the next section.
Detection signals
How to detect CWE-304
CWE-304
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Frequently asked questions What is CWE-304?
How serious is CWE-304?
What languages or platforms are affected by CWE-304?
How can I prevent CWE-304?
How does Plexicus detect and fix CWE-304?
Where can I learn more about CWE-304?
Frequently asked questions
What is CWE-304?
This vulnerability occurs when a software authentication process omits a required step, weakening its overall security.
How serious is CWE-304?
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-304?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-304?
Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.
How does Plexicus detect and fix CWE-304?
Plexicus's SAST engine matches the data-flow signature for CWE-304 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-304?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/304.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Ready to validate what matters?
Ready to validate what matters?
Plexicus is Proof-Driven AppSec: validated findings, contextual understanding, and reviewed remediation — anchored in evidence, scoped with you.