A critical stack-based Buffer Overflow vulnerability has been discovered in SonicWall VPNs. When exploited, it allows unauthenticated remote attackers to execute arbitrary code on the impacted devices.

Tracked as CVE-2020-5135, the vulnerability impacts multiple versions of SonicOS ran by hundreds of thousands of active VPNs.

Craig Young of Tripwire Vulnerability and Exposure Research Team (VERT) and Nikita Abramov of Positive Technologies have been credited with discovering and reporting the vulnerability.

Shodan lists over 800,000 devices

Given an increase in employees working remotely and the reliance on corporate VPNs, easily exploitable flaws like these are concerning when it comes to security.

As confirmed by Tenable researchers as of today, Shodan shows over 800,000 VPN devices running vulnerable SonicOS software versions, depending on the search term used.

Although a Proof-of-Concept (POC) exploit is not yet available in the wild, the vast attack surface available to adversaries means companies should upgrade their devices immediately.

https://csirt.cy/wp-content/uploads/2020/10/Screenshot-2020-10-16-at-9_20_53-am-300x182.png 300w, https://csirt.cy/wp-content/uploads/2020/10/Screenshot-2020-10-16-at-9_20_53-am-1024x621.png 1024w, https://csirt.cy/wp-content/uploads/2020/10/Screenshot-2020-10-16-at-9_20_53-am-768x466.png 768w, https://csirt.cy/wp-content/uploads/2020/10/Screenshot-2020-10-16-at-9_20_53-am-1536x931.png 1536w" alt="" width="1005" height="609" class="wp-image-7163 aligncenter" style="box-sizing: border-box; border: 0px; vertical-align: middle; clear: both; display: block; margin: 0px auto; height: auto; max-width: 100%; color: rgb(51, 51, 51); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;" loading="lazy" />

Potentially exploitable devices listed on Shodan running vulnerable SonicOS versions

Impacted versions and remediation guidance

The following SonicWall VPN devices are impacted by CVE-2020-5135:

“SonicWall has released updates to remediate this flaw. SSL VPN portals may be disconnected from the Internet as a temporary mitigation before the patch is applied,” stated Tripwire VERT’s advisory.

The following versions are available to upgrade to for safeguarding against this vulnerability:

Provided the vast number of devices that are still running the outdated SonicOS versions and the critical nature of this vulnerability, complete research findings on CVE-2020-5135 are expected to be released once enough users have patched their systems.

The information contained in this website is for general information purposes only. The information is gathered from BLEEPING COMPUTER, while we endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the website or the information, products, services, or related graphics contained on the website for any purpose. Any reliance you place on such information is therefore strictly at your own risk.  Through this website, you are able to link to other websites which are not under the control of CSIRT-CY. We have no control over the nature, content and availability of those sites. The inclusion of any links does not necessarily imply a recommendation or endorse the views expressed within them. Every effort is made to keep the website up and running smoothly. However, CSIRT-CY takes no responsibility for, and will not be liable for, the website being temporarily unavailable due to technical issues beyond our control.