Microsoft Issues Rare Patch for Wireless Keyboard Flaw

So much for a spring break: Microsoft today dropped 67 security patches in its April Patch Tuesday release, including one for a piece of one of its hardware devices, the Wireless Keyboard 850.

Hardware – and keyboard – patches are relatively rare, so the security bypass vulnerability Microsoft fixed today in the keyboard stood out among the typical security flaws, which included 24 critical bugs, 42 rated as important, and one as moderate. Microsoft rated the keyboard vuln (CVE-2018-8117) as "important."

The flaw allows an attacker to reuse the keyboard's AES encryption key in order to log keystrokes, or inject them into the affected keyboard devices. According to Microsoft, "an attacker could simulate keystrokes to send malicious commands into a victim's computer" or "read keystrokes such as passwords sent by other keyboards for the affected devices."

Such an attack would be no simple feat: it requires physical proximity, and the attacker would have to pilfer the encryption key from the vulnerable keyboard. The patch forces each wireless keyboard to generate a unique AES encryption key.

Dustin Childs, communications manager for ZDI, says keyboard patching is rare, mainly because most vendors of the hardware devices don't have the update infrastructure like Microsoft has nor the ability to track them for updates. "Microsoft has the operating system where it can update" them, Childs notes. While the attack would require some finesse and sophistication, it's still worth applying the patch in short order, albeit not as a top priority compared with other updates in this month's patch batch, according to Childs.

"If I know I have this keyboard in my enterprise, I'm not going to ignore this patch," he says, noting that open work environments would be more at risk of such an attack.

Microsoft didn't detail how an attacker would steal the encryption key. But Jimmy Graham, director of product management at Qualys, says it appears to be a hardware or side-channel attack, based on the way Microsoft is blocking access to the key with the fix.

Graham points out that most of the critical bugs patched today have to do with browsers. He recommends those patches as priority for endpoints.

Microsoft also patched five critical flaws in the Windows Font Library that each allow remote code execution via Web or file-sharing attacks. Both Graham and Childs consider these patches priorities as well. "Browser [updates] are always important and near the top" as a priority, Childs says.

The Microsoft Graphics Remote Code Execution vuln flaws: CVE-2018-1010, CVE-2018-1012, CVE-2018-1013, CVE-2018-1015, and CVE-2018-1016 could allow an attacker to tuck malicious code into fonts. Malicious fonts can be used in Web browsing and documents and attachments.

"According to Microsoft, these vulnerabilities can be exploited through a Web-based attack, meaning the user only needs to visit a malicious Web page. This could be through a compromised site or malicious ad server," Qualys' Graham says. "The other attack vector is file-based, meaning a document could be sent via email or through a fileshare that would run the exploit if opened."

Childs says these flaws are reminiscent of the Duqu nation-state group's methods. The attackers behind Duqu embedded the Duqu dropper into type fonts via the Win32k TrueType font parsing engine. "Fonts are everywhere, so always put these" vulns at a high priority, he says.

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