PT-2026-36665 — Rubygems Openc3

PT-2026-36665 · Rubygems · Openc3

Published

2026-04-22

Updated

2026-04-22

CVSS v3.1

8.1

High

Vector

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Summary

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.

Details

The design flaw in authentication model (authentication.rb) allows for interchangeable use of password and session tokens for user authentication As old tokens are not revoked upon password reset, an attacker who has obtained a valid session token can continue to authenticate and change the account’s password even after the victim resets it, thereby maintaining persistent control over the compromised account.

PoC

Attacker is logged in user account with hijacked valid session token, but not knowing the actual password
Legitimate user, as preventive action, changes his password ( password123 ) using old password ( password ), that he knows, then establishes new session
Attacker issues another password change request (in web proxy like Burp) supplying his still valid token as old password , changing it to attacker-password, from this point preventing any other legitimate users from accessing account