Jivejdon EUVD-2026-95308

Exploitation requires that the target Jivejdon account was created through the Sina Weibo OAuth login flow (SinaUserCallBackAction / OAuthAccountServiceImp.transferSina), since only those accounts have passwords set to the first four digits of the user's Weibo ID; accounts created by other means are not affected. The attacker must also know or enumerate the victim's public Weibo user ID. Beyond that there are no limiting factors - no authentication, no user interaction, and no non-default configuration is needed to perform the form login once the derived credential is known, so any internet-reachable Jivejdon instance using the Weibo integration is exposed.

The CVSS 4.0 score of 6.9 (Medium) is driven by a fully remote, low-complexity, unauthenticated attack vector (AV:N/AC:L/AT:N/PR:N/UI:N) with limited confidentiality and integrity impact (VC:L/VI:L) and no availability or subsequent-system impact. The flaw is a genuine design weakness (CWE-1391, weak/predictable credentials): OAuthAccountServiceImp.transferSina() derives a password from the first four digits of a public Weibo ID, so the credential entropy is only ~10,000 combinations and often directly guessable. No EPSS score, CISA KEV entry, or published exploit code was provided in the input, so despite the trivial exploit logic there is no evidence of active exploitation or weaponization. The practical impact is bounded to accounts that were actually created via the Sina/Weibo OAuth flow - a victim pool limited to deployments using that integration - which tempers the otherwise-easy exploitability. Net assessment: a real and easily-understood authentication-bypass bug credibly reported by VulnCheck, but the Medium (not Critical) severity and the extremely small real-world deployment footprint of Jivejdon make this a low operational priority for most organizations.

An attacker enumerates a public Sina Weibo user ID of a victim who has a Jivejdon account provisioned through the Weibo OAuth login, computes the password as the first four digits of that Weibo ID, and simply logs in through the normal form-login page. Once authenticated as the victim, the attacker reads the victim's private content and posts forum messages under their identity. No published exploit tool is required - the attack is manual and follows directly from the VulnCheck advisory's description of the credential-derivation logic.