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.

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.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
cotonti cotonti unaffected
Version Status Constraints
0 affected ≤ 1.0.0

No data.

No data.

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Project Subscriptions

Vendors Products
Cotonti Subscribe
Cotonti Siena Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

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

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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

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

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

Link: CVE-2026-121553

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses