CVE-2026-42084: OpenC3 COSMOS: Hijacked session token can be used to reset password for persistence

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-04 · updated 2026-10-26
Weakness: CWE-620

Description

OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. Prior to versions 6.10.5 and 7.0.0-rc3, the OpenC3 password change functionality allows a user to change their password without providing the old password, by accepting a valid session token instead. In assumed breach scenarios, this behaviour can be exploited by an attacker who has already obtained a valid session token, to gain persistence in hijacked account (including admin) and prevent legitimate users from accessing the account. This issue has been patched in versions 6.10.5 and 7.0.0-rc3.

Affected products

OpenC3 cosmos: before 6.10.5; 7.0.0-rc1, 7.0.0-rc2 — fixed in 6.10.5

How to fix

Upgrade to a fixed version: OpenC3 cosmos 6.10.5. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-42084 or the next vulnerability affects your stack