# CVE-2026-121553: Cotonti weak token generation in user registration

Source: https://junglewise.ai/threats/cve-2026-121553-cotonti-through-1-0-0-generates-registration-and-email-change  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-03. Updated: 2026-11-03  
License: CC BY 4.0 with a link back

CVE-2026-121553 · Severity: medium · CVSS 4.8 · Published 2026-11-03

Cotonti, a PHP content management system, uses a weak method (MD5 hash of microtime) to generate email validation tokens for user registration and email changes. Attackers can predict these tokens by deriving the generation time from HTTP response headers and computing candidate tokens offline, allowing them to activate accounts or confirm email addresses they do not control without owning those email addresses.

Technologies: [Cotonti](https://junglewise.ai/threats/technologies/cotonti). Vendors: [Cotonti](https://junglewise.ai/threats/vendors/cotonti).

## Quick answers

**Is CVE-2026-121553 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121553 being exploited in the wild.

**How severe is CVE-2026-121553?** Medium severity, with a CVSS score of 4.8, published 3 November 2026.

**Which products and versions are affected?** Cotonti through 1.0.0.

**Is there a fix for CVE-2026-121553?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-121553 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-121553?** Check whether you run Cotonti at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a cryptographic weakness in token generation: Cotonti uses md5(microtime()) to create validation tokens for account registration and email-change verification. An attacker can estimate the generation time from the HTTP Date header, compute candidate tokens offline with a small time window, and submit valid tokens to users.register.php to bypass email-ownership verification. The attack requires no authentication or user interaction beyond submitting a prediction attempt.

## Affected products

- Cotonti Cotonti through 1.0.0

## Timeline

- 2026-11-03: disclosed

## References

- [https://github.com/Cotonti/Cotonti](https://github.com/Cotonti/Cotonti)
- [https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.functions.php](https://github.com/Cotonti/Cotonti/blob/1.0.0/modules/users/inc/users.functions.php)

## Related threats

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- [Cotonti cross-site request forgery in extensions manager](https://junglewise.ai/threats/cve-2026-100524-cotonti-through-1-0-0-contains-a-cross-site-request-forgery)
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- [Cotonti reflected cross-site scripting in message.php](https://junglewise.ai/threats/cve-2026-100522-cotonti-through-1-0-0-contains-a-reflected-cross-site-scripting)
- [Cotonti reflected cross-site scripting in search plugin](https://junglewise.ai/threats/cve-2026-100521-cotonti-through-1-0-0-contains-a-reflected-cross-site-scripting)