Critical Zero-Day Pre-authentication Remote Code Execution Exploit Published for 5.x Versions of vBulletin
New critical zero-day pre-auth RCE exploit code published on Full Disclosure mailing list for 5.x versions of vBulletin (CVE-2019-16759).
UPDATE 09/25/2019: The background and solution sections below have been updated to reflect the security patch issued by the vBulletin team.
Background
A preauthentication remote code execution (RCE) zero-day exploit was recently disclosed anonymously for vBulletin 5.x. This zero-day does not seem to have followed coordinated disclosure procedures. VBulletin released a new security patch for vBulletin versions 5.5.2, 5.5.3, and 5.5.4.
Analysis
Tenable Research has analyzed and confirmed that this exploit works on default configurations of vBulletin. Based on the public PoC, an unauthenticated attacker can send a specially crafted HTTP POST request to a vulnerable vBulletin host and execute commands. These commands would be executed with the permissions of the user account that the vBulletin service is utilizing. Depending on the service user’s permissions, this could allow complete control of a host.
Proof of concept
The published exploit code returns its successful execution in a JSON formatted response.
Solution
The vBulletin team has issued a patch for CVE-2019-16759 for vBulletin versions 5.5.2, 5.5.3, and 5.5.4. Users on earlier versions of vBulletin 5.x will need to update to one of the currently supported versions in order to apply the patch. VBulletin cloud users don’t need to perform any additional actions as the fix has already been applied to the cloud version.
Identifying affected systems
A list of Tenable plugins to identify this vulnerability will appear here as they’re released.
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Ryan Seguin
Security Response Manager
Ryan joined Tenable in 2013 as a customer support engineer assisting customers with technical troubleshooting and product education. After that, he helped create dashboard and report templates for SecurityCenter that users can download through the Tenable.sc feed. Now Ryan is a member of the Security Response team, informing customers of the latest security threats, and providing in-depth analytics for today’s most critical vulnerabilities.
Interests outside of work: Ryan is a retro video game console/arcade hardware enthusiast and modder, and he is also studying Japanese and hopes to one day be fluent.
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