CVE-2026-121553

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.

• CWE-338

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

Published

Nov 3, 2026

Last Modified

Nov 3, 2026

Status

Deferred

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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