An issue was discovered in Mbed TLS before 3.6.6 and 4.x before 4.1.0 and TF-PSA-Crypto before 1.1.0. There is a Predictable Seed in a Pseudo-Random Number Generator (PRNG).
The following code is for security research and authorized testing only.
python
/*
* PoC Concept for CVE-2026-34871: Predictable Seed in PRNG
* This C code demonstrates the consequence of a predictable seed (e.g., time) in a PRNG.
* If Mbed TLS uses a predictable seed, the output sequence becomes reproducible.
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void simulate_vulnerable_prng() {
// Scenario: Using system time as a seed (Predictable)
unsigned int predictable_seed = (unsigned int)time(NULL);
printf("[+] Using predictable seed: %u\n", predictable_seed);
srand(predictable_seed);
printf("[+] Generated Random Numbers: ");
for (int i = 0; i < 5; i++) {
printf("%d ", rand());
}
printf("\n");
printf("[!] An attacker knowing the time of generation can reproduce this sequence.\n");
}
int main() {
simulate_vulnerable_prng();
return 0;
}