This vBulletin vBug is vBad: Zero-day exploit lets miscreants hijack vulnerable web forums

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An anonymous bug hunter has publicly disclosed a zero-day flaw in the version 5 of the popular vBulletin forum software than can be exploited over the internet to hijack servers. No patch is known to be available.

The security hole was revealed last night in a post to the Full Disclosure mailing list: the message exactly explains how a simple HTTP POST request can be abused by an attacker to remotely execute commands on the targeted vBulletin server without any authentication. That would allow hackers to commandeer web servers powering the forum software, steal data, tamper with information, launch assaults on other systems, and so on.

It can be done in fewer than 20 lines of Python code. This is a very, very, bad thing.

The zero-day exploit code is verified to work against supported versions of vBulletin from 5.0.0 to the latest 5.5.4 build.

The Register has asked vBulletin for comment on the report, or an estimate on when a fix could be out, but so far we have yet to hear back.

Meanwhile, security professionals are marveling at the simplicity of the exploit and the extent to which vulnerable boards can be owned by the attack.

lol wait is this literally just throwing a command in a request and it executing? am i missing here

— 𝔞𝔫𝔵𝔦𝔢𝔱𝔶 𝔭𝔦𝔡𝔤𝔢𝔬𝔫 (@da_snowbird) September 24, 2019

Websites running vBulletin version 5, first released in 2012, are advised to keep a close eye on their servers and make sure that nobody is attempting to exploit the vulnerability and use it as a springboard for further attacks. Better yet, maybe just pull the plug completely until a fix or mitigation lands.

Unfortunately, as security researchers have noted, vBulletin’s customer base includes a number of large companies, sports teams, and entertainment groups that are likely now exposed until such time as the developer can figure out a fix. ®