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CVE-2021-4240

CVE-2021-4240:
Insufficient Entropy in PHPServerMon PRNG

5.3

CVSS Score
3.1

Basic Information

CVE ID
CVE-2021-4240
GHSA ID
GHSA-97w9-gcc7-vr8g
EPSS Score
0.48943%
CWE
CWE-330
Published
11/16/2022
Updated
7/19/2023
KEV Status
No
Technology
TechnologyPHP

Technical Details

CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Package NameEcosystemVulnerable VersionsFirst Patched Version
phpservermon/phpservermoncomposer< 3.6.03.6.0

Vulnerability Intelligence
Miggo AIMiggo AI

Miggo AIRoot Cause Analysis

The vulnerability stems from the pre-patch implementation of generatePasswordResetToken which used sha1(uniqid(mt_rand(), true)). mt_rand() is cryptographically insecure and produces predictable values. The commit 3daa804 explicitly replaces mt_rand with cryptographically secure random_bytes, and CWE-1241 specifically calls out 'Use of Predictable Algorithm in Random Number Generator'. The function's security-critical context (password reset tokens) combined with the documented fix confirms this as the vulnerable function.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

WAF Protection Rules

WAF Rule

* vuln*r**ility, w*i** w*s *l*ssi*i** *s pro*l*m*ti*, w*s *oun* in p*ps*rv*rmon. T*is *****ts t** *un*tion `**n*r*t*P*sswor*R*s*tTok*n` o* t** *il* `sr*/psm/S*rvi**/Us*r.p*p`. T** m*nipul*tion l***s to us* o* pr**i*t**l* *l*orit*m in r*n*om num**r **

Reasoning

T** vuln*r**ility st*ms *rom t** pr*-p*t** impl*m*nt*tion o* **n*r*t*P*sswor*R*s*tTok*n w*i** us** s***(uniqi*(mt_r*n*(), tru*)). mt_r*n*() is *rypto*r*p*i**lly ins**ur* *n* pro*u**s pr**i*t**l* v*lu*s. T** *ommit ******* *xpli*itly r*pl***s mt_r*n*