"This is the pre-exploit window to patch slamming shut right in front of your eyes," wrote Chris Krebs, the head of the Cybersecurity and Infrastructure Security Agency, in a tweet Sunday afternoon. "If you didn’t patch by this morning, assume compromised."The HackThe F5 vulnerability, first discovered and disclosed to F5 by cybersecurity firm Positive Technologies, affects a series of so-called BIG-IP devices that act as load balancers within large enterprise networks, distributing traffic to different servers that host applications or websites. Positive Technologies found a so-called directory traversal bug in the web-based management interface for those BIG-IP devices, allowing anyone who can connect to them to access information they're not intended to. That vulnerability was exacerbated by another bug that allows an attacker to run a "shell" on the devices that essentially lets a hacker run any code on them that they choose.
The result is that anyone who can find an internet-exposed, unpatched BIG-IP device can intercept and mess with any of the traffic it touches. Hackers could, for instance, intercept and redirect transactions made through a bank's website, or steal users' credentials. They could also use the hacked device as a hop point to try to compromise other devices on the network. Since BIG-IP devices have the ability to decrypt traffic bound for web servers, an attacker could even use the bug to steal the encryption keys that guarantee the security of an organization's HTTPS traffic with users, warns Kevin Gennuso, a cybersecurity practitioner for a major American retailer. "It's really, really powerful," says Gennuso, who declined to name his employer but said that he'd spent much of the holiday weekend working to fix the security vulnerabilities in its F5 devices. "This is probably one of the most impactful vulnerabilities I’ve seen in my 20-plus years of information security, because of its depth and breadth and how many companies use these devices."
When reached for comment, F5 directed WIRED to a security advisory the company posted on June 30. "This vulnerability may result in complete system compromise," the page reads, before going on to detail how companies can mitigate it.
How Serious Is This?F5's bug is particularly concerning because it's relatively easy to exploit while also offering a large menu of options to hackers. Security researchers have pointed out that the URL that triggers the vulnerability can fit into a tweet—one researcher from South Korea's Computer Emergency Response Team posted a two versions in a single tweet along with a video demo. Since the attack targets a vulnerable device's web interface, it can be pulled off in its simplest form just by tricking someone into visiting a carefully crafted URL.