CVE-2026-121553
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in. Limited direct impact.
- Exploit odds
- 0.4% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- ReservedThe CVE id was reserved by its CNA
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.4% in the next 30 days (EPSS).
- Severity: 6.3 MEDIUM (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.4% · EPSS, next 30 days
- Weakness
- CWE-338
- Record status
- Deferred
Attack profile CVSS 4.0 · 6.3
- Attack vector
- Network
- Complexity
- High
- Attack requirements
- None
- Privileges needed
- None
- User interaction
- None
- Confidentiality
- None
- Integrity
- Low
- Availability
- Low
Raw 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-121553.md and follow it. Check whether this project is affected by CVE-2026-121553. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
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
- https://github.com/Cotonti/Cotonti/issues/1904