Cotonti through 1.0.0 generates registration and email-change validation tokens with md5(microtime()), allowing attackers to bypass email-ownership verification by predicting tokens. Attackers can derive the generation time from the HTTP Date header and compute candidate tokens offline. They then submit these tokens to the users.register.php validate handler to activate accounts or confirm email addresses they do not control.

Metrics

Attack Vector Network

Attack Complexity High

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact Low

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact Low

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploitation poc

Automatable no

Technical Impact partial

Affected Vendors & Products

Vendors Products
Cotonti
  • Cotonti
  • Cotonti Siena

No data.

No data.

References
Link Providers
https://github.com/Cotonti/Cotonti cve-icon cve-icon
https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.functions.php#L97 cve-icon cve-icon
https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.profile.php#L116 cve-icon cve-icon
https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.register.php#L148 cve-icon cve-icon
https://github.com/Cotonti/Cotonti/issues/1904 cve-icon cve-icon cve-icon
https://github.com/Cotonti/Cotonti/pull/1905 cve-icon cve-icon
https://www.vulncheck.com/advisories/cotonti-through-1.0.0-predictable-validation-tokens-via-md5-microtime cve-icon cve-icon
History

Sat, 07 Nov 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 03 Nov 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Cotonti cotonti
Vendors & Products Cotonti cotonti

Tue, 03 Nov 2026 15:30:00 +0000

Type Values Removed Values Added
Description Cotonti through 1.0.0 generates registration and email-change validation tokens with md5(microtime()), allowing attackers to bypass email-ownership verification by predicting tokens. Attackers can derive the generation time from the HTTP Date header and compute candidate tokens offline. They then submit these tokens to the users.register.php validate handler to activate accounts or confirm email addresses they do not control.
Title Cotonti through 1.0.0 Predictable Validation Tokens via md5(microtime())
First Time appeared Cotonti
Cotonti cotonti Siena
Weaknesses CWE-338
CPEs cpe:2.3:a:cotonti:cotonti_siena:*:*:*:*:*:*:*:*
Vendors & Products Cotonti
Cotonti cotonti Siena
References
Metrics cvssV3_1

{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N'}
cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published: 2026-11-03T15:17:11.513Z

Updated: 2026-11-07T03:09:49.080Z

Reserved: 2026-11-03T14:46:15.628Z

Link: CVE-2026-121553

cve-icon Vulnrichment

Updated: 2026-11-07T03:09:42.537Z

cve-icon NVD

Status : Deferred

Published: 2026-11-03T16:17:27.437

Modified: 2026-11-07T04:17:22.123

Link: CVE-2026-121553

cve-icon Redhat

No data.