Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-333 Variant Draft
Improper Handling of Insufficient Entropy in TRNG
This vulnerability occurs when a system fails to properly manage the limited or unpredictable output rate of a true random number generator (TRNG), potentially causing failures, delays, or weakened…
Definition
What is CWE-333?
This vulnerability occurs when a system fails to properly manage the limited or unpredictable output rate of a true random number generator (TRNG), potentially causing failures, delays, or weakened security.
True Random Number Generators (TRNGs) rely on unpredictable physical processes, like electronic noise, to produce entropy. Unlike software-based generators, their output rate is inherently limited and can sometimes stall if the entropy source is exhausted, causing applications to hang or fail when they demand random data faster than the hardware can supply.
For security-critical operations, such as cryptographic key generation or session token creation, this limitation is a major risk. Developers must design their systems to handle these slow or blocked states gracefully—for example, by using TRNG output only to seed cryptographically secure pseudorandom number generators (CSPRNGs)—and avoid using TRNGs directly in performance-sensitive or synchronous loops where a delay could break functionality.
Real-world impact
Real-world CVEs caused by CWE-333
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
This code uses a TRNG to generate a unique session id for new connections to a server:
while (1){
if (haveNewConnection()){
if (hwRandom()){
int sessionID = hwRandom();
createNewConnection(sessionID);
} } } 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-333
- Implementation Rather than failing on a lack of random numbers, it is often preferable to wait for more numbers to be created.
Detection signals
How to detect CWE-333
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.
CWE-333
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-333?
How serious is CWE-333?
What languages or platforms are affected by CWE-333?
How can I prevent CWE-333?
How does Plexicus detect and fix CWE-333?
Where can I learn more about CWE-333?
Frequently asked questions
What is CWE-333?
This vulnerability occurs when a system fails to properly manage the limited or unpredictable output rate of a true random number generator (TRNG), potentially causing failures, delays, or weakened security.
How serious is CWE-333?
MITRE rates the likelihood of exploit as Low — exploitation is uncommon, but the weakness should still be fixed when discovered.
What languages or platforms are affected by CWE-333?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-333?
Rather than failing on a lack of random numbers, it is often preferable to wait for more numbers to be created.
How does Plexicus detect and fix CWE-333?
Plexicus's SAST engine matches the data-flow signature for CWE-333 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-333?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/333.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-333
CWE-331 Parent
Insufficient Entropy
This vulnerability occurs when a system's random number generator or algorithm lacks sufficient unpredictability, creating patterns or…
CWE-332 Sibling
Insufficient Entropy in PRNG
This vulnerability occurs when a Pseudo-Random Number Generator (PRNG) doesn't have enough randomness (entropy) to start with, or isn't…
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