Savitech drivers used by several companies that provide specialized audio products expose computers to hacker attacks by installing a new root certificate into the Trusted Root Certification Authorities store in Windows.
The USB audio drivers from Savitech, a company that offers application-specific integrated circuits for audio and video solutions, are used by several vendors. The CERT Coordination Center lists products from Accuphase, AsusTek, Audio-Technica, Creek Audio, EMC, FiiO Electronics, HiFime, Intos, JDS Labs, McIntosh Laboratory, ShenZhen YuLong Audio, Stoner Acoustics, Sybasonic, and TeraDak Audio as possibly being affected.
Savitech used the “SaviAudio” root certificate as part of its effort to support the outdated Windows XP operating system, but the certificate is no longer installed by the latest version of the drivers released by the company.
According to RSA’s Kent Backman, the researcher who discovered the flaw, self-signed root certificates were silently installed by the packages provided by Savitech between 2013 and 2017.
Installing such a certificate allows hackers who are in possession of the Savitech private key to impersonate online services, sign malicious software, and decrypt network traffic via man-in-the-middle (MitM) attacks.
While this worst case scenario sounds serious, in reality, the risk of an attack is low as, hopefully, Savitech has taken steps to ensure that the private key cannot be obtained easily by malicious actors. CERT/CC noted that there is no evidence of the key being compromised.
The vulnerability, tracked as CVE-2017-9758 and dubbed by RSA “Inaudible Subversion,” was introduced by Savitech in an attempt to seamlessly support Windows XP, which Microsoft abandoned several years ago.
While users still running Windows XP are exposed to attacks due to much more serious vulnerabilities left unpatched in the operating system, the audio drivers install the root certificate on newer versions of Windows as well, despite not being needed.
“In the big picture of things, we think that Inaudible Subversion may be a vulnerability of low–if any–consequence, but illustrates the influence of market forces behind hardware vendor sustainment of a still-popular operating system that is no longer supported by Microsoft,” Backman said in a blog post.
Version 184.108.40.206 or later of the Savitech drivers no longer install the root certificate, but they do not remove the existing certificate. Users have been advised to manually remove previously installed certificates.
The root certificate installed by the audio drivers was configured to trust any certificate issued by the SaviAudio CA for “All” purposes. This is typical of certificates issued by Microsoft itself or certificates used by security products for SSL traffic inspection. While the use of root certificates for traffic inspection by security products is considered acceptable, tests have shown that some implementations actually weaken HTTPS security. On the other hand, root certificates installed by any other software pose serious security and privacy risks.