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-321 Variant Draft
Use of Hard-coded Cryptographic Key
This vulnerability occurs when an application embeds a fixed, unchangeable cryptographic key directly within its source code or configuration files.
Definition
What is CWE-321?
This vulnerability occurs when an application embeds a fixed, unchangeable cryptographic key directly within its source code or configuration files.
Hard-coding cryptographic keys is a common but dangerous practice that undermines the security of encrypted data. Since the key is the same in every instance of the application and cannot be changed without modifying the code, an attacker who discovers the key (e.g., by inspecting the source code, binaries, or configuration files) can decrypt any sensitive data the application protects. This flaw effectively renders encryption useless, as the secret is no longer secret.
To fix this, developers should use secure key management systems that allow keys to be stored externally, rotated regularly, and accessed securely at runtime. While SAST tools can detect the hard-coded pattern, Plexicus uses AI to suggest the actual code fix—such as integrating with a secrets manager or environment variables—saving hours of manual refactoring and helping you enforce secure key handling across your entire application portfolio.
Real-world impact
Real-world CVEs caused by CWE-321
-
Engineering Workstation uses hard-coded cryptographic keys that could allow for unathorized filesystem access and privilege escalation
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Remote Terminal Unit (RTU) uses a hard-coded SSH private key that is likely to be used by default.
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WiFi router service has a hard-coded encryption key, allowing root access
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Communications / collaboration product has a hardcoded SSH private key, allowing access to root account
How attackers exploit it
Step-by-step attacker path
- 1
The following code examples attempt to verify a password using a hard-coded cryptographic key.
- 2
The cryptographic key is within a hard-coded string value that is compared to the password. It is likely that an attacker will be able to read the key and compromise the system.
- 3
In 2022, the OT:ICEFALL study examined products by 10 different Operational Technology (OT) vendors. The researchers reported 56 vulnerabilities and said that the products were "insecure by design" [REF-1283]. If exploited, these vulnerabilities often allowed adversaries to change how the products operated, ranging from denial of service to changing the code that the products executed. Since these products were often used in industries such as power, electrical, water, and others, there could even be safety implications.
- 4
Multiple vendors used hard-coded keys for critical functionality in their OT products.
Vulnerable code example
Vulnerable C
The following code examples attempt to verify a password using a hard-coded cryptographic key.
int VerifyAdmin(char *password) {
if (strcmp(password,"68af404b513073584c4b6f22b6c63e6b")) {
printf("Incorrect Password!\n");
return(0);
}
printf("Entering Diagnostic Mode...\n");
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-321
- Architecture and Design Prevention schemes mirror that of hard-coded password storage.
Detection signals
How to detect CWE-321
CWE-321
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Frequently asked questions What is CWE-321?
How serious is CWE-321?
What languages or platforms are affected by CWE-321?
How can I prevent CWE-321?
How does Plexicus detect and fix CWE-321?
Where can I learn more about CWE-321?
Frequently asked questions
What is CWE-321?
This vulnerability occurs when an application embeds a fixed, unchangeable cryptographic key directly within its source code or configuration files.
How serious is CWE-321?
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-321?
MITRE lists the following affected platforms: ICS/OT.
How can I prevent CWE-321?
Prevention schemes mirror that of hard-coded password storage.
How does Plexicus detect and fix CWE-321?
Plexicus's SAST engine matches the data-flow signature for CWE-321 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-321?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/321.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-321
CWE-798 Parent
Use of Hard-coded Credentials
This vulnerability occurs when software contains built-in, unchangeable authentication secrets like passwords or encryption keys within…
CWE-259 Sibling
Use of Hard-coded Password
This vulnerability occurs when an application embeds a password directly into its source code or configuration files. This hard-coded…
Resources
Further reading
- MITRE — official CWE-321 https://cwe.mitre.org/data/definitions/321.html
- The CLASP Application Security Process https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf
- OT:ICEFALL: The legacy of "insecure by design" and its implications for certifications and risk management https://www.forescout.com/resources/ot-icefall-report/
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