There’s rarely any real justification for letting a vulnerability with a 10.0 rating go unchecked, though some organizations do just that with alarming frequency. But one such bug in the Out-of-Band Access Point (AP) Image Download feature of Cisco IOS XE Software for Wireless LAN Controllers (WLCs) bears scrutiny and implementing a quick fix.
If not addressed, unauthenticated, remote attackers could upload arbitrary files to systems affected by a hard-coded JSON Web Token, Cisco says. All an attacker would need to do to successfully exploit is send crafted HTTPS requests to the AP image download interface. Once done, the miscreants could not only upload files but could execute path reversal as well “as arbitrary commands with root privileges.”
The vulnerability earned its severity score “because it allows unauthenticated attackers to remotely upload and execute files on widely deployed Cisco infrastructure,” says Shane Barney, CISO at Keeper Security.
“At the root is a hard-coded JWT secret, which could enable a remote, unauthenticated attacker to upload arbitrary files, achieve path traversal and execute arbitrary commands with root privileges on affected devices – a serious risk for any organization relying on these devices,” he explains.
Although Cisco has issued free software updates, noting that there was no work-around, concerns about the vulnerability’s risk ratcheted higher late last week after an analysis by Ziad Badawi at horizon.ai underscored “how a combination of hard-coded secrets, insufficient input validation and exposed endpoints can lead to serious security risks—even in widely deployed enterprise infrastructure.”
The flaw “lets attackers upload anything they want to your wireless controllers, and if the right feature is on, they can even run commands as if they owned the device—no password needed,” says J Stephen Kowski, field CTO at SlashNext.
And that’s because of a secret code “that’s not really secret, so anyone with the know-how can make their own access pass.”
Bugcrowd founder Casey Ellis calls the vulnerability “a classic example of why hardcoded secrets and inadequate validation are such dangerous anti-patterns in software security,” noting that “the real danger lies in the accessibility and criticality of the affected systems.”
The fact that Cisco IOS XE is widely deployed in enterprise and service provider environments is particularly dangerous. “A successful exploit could lead to significant disruption or compromise of sensitive data,” says Ellis.
The security experts are all in agreement that organizations should rush to fix the vulnerability.
Patching is urgent, says Kowski, “since bad guys could take over your network by just sending a few messages.” In real life, security teams, need to “keep an eye on who’s trying to upload files or use weird access codes,” which could “help stop trouble before it starts.”
Noting that the “severity and ease of exploitation” should make patching “an immediate top priority for all organizations using Cisco IOS XE WLC devices,” Barney urged security teams to “review Cisco’s official advisory, apply the recommended mitigations and patches and audit access logs for any signs of unauthorized JWT usage or unusual file uploads.”
He also advised eliminating “hard-coded secrets from authentication workflows, enforcing robust file upload validation and path sanitization and maintaining continuous monitoring and patch management across all critical systems.”
Ellis says security teams must bear in mind that “this is a 10.0 CVSS vulnerability for a reason — it’s both easy to exploit and has severe consequences. For security teams, the priority is clear: patch as soon as possible,” he says.
If organizations find that patching “isn’t conceivable in the short term,” they must implement “compensating controls such as restricting access to the affected endpoints, monitoring for suspicious file uploads and disabling unnecessary services.”
