CVSS 4.0
6.3 mediumCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:NCVE-2026-121553
Medium (6.3). EPSS 0.4% estimated probability of exploitation activity in the next 30 days.
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.
Severity
CVSS 3.1
4.8 mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L- EPSS
- 0.4% estimated probability of exploitation activity in the next 30 days; 29th percentile. Scored 2026-11-05. A forecast for this CVE across the internet, not for your own systems.
- CWE
- CWE-338 Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
- OWASP Top 10
- A04:2025 Cryptographic Failures
- Published
- Modified
- Record from
- the NVD, synced
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Explain CVE-2026-121553 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-121553?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-121553?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-121553 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| cotonti | through 1.0.0 |
References
- 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