CVE-2021-4240Network attack vector

Account access via predictable password-reset tokens

Published Nov 15, 2022 · Updated Apr 15, 2025

Predictable password-reset tokens in PHP Server Monitor before 3.6.0 allow remote attackers to access another user's account. The generatePasswordResetToken method in src/psm/Service/User.php hashes uniqid output seeded with mt_rand, whose output is predictable rather than cryptographically secure. Exploitation requires knowledge of the generator state to predict a valid emailed reset token; the reported impact is limited to unauthorized disclosure through the affected account.

CVSS severity2.6
Low
EPSS probability0.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Predictable password-reset tokens in PHP Server Monitor before 3.6.0 allow remote attackers to access another user's account. The generatePasswordResetToken method in src/psm/Service/User.php hashes uniqid output seeded with mt_rand, whose output is predictable rather than cryptographically secure. Exploitation requires knowledge of the generator state to predict a valid emailed reset token; the reported impact is limited to unauthorized disclosure through the affected account.

The record

CVE
CVE-2021-4240
Published
Nov 15, 2022
Updated
Apr 15, 2025
Vendor
PHP Server Monitor
Product
PHP Server Monitor
Classifications
CWE-1241, CWE-330, CWE-331, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 15, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PHP Server Monitor · PHP Server Monitorversion=n/a

Published CVSS scores

2.6VulDB CNACVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1241Use of Predictable Algorithm in Random Number Generator
CWE-330Use of Insufficiently Random Values
CWE-331Insufficient Entropy
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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