Researchers say that nearly 336,000 devices exposed to the Internet remain vulnerable to a critical vulnerability in firewalls sold by Fortinet because admins have yet to install patches the company released three weeks ago.

CVE-2023-27997 is a remote code execution in Fortigate VPNs, which are included in the company’s firewalls. The vulnerability, which stems from a heap overflow bug, has a severity rating of 9.8 out of 10. Fortinet released updates silently patching the flaw on June 8 and disclosed it four days later in an advisory that said it may have been exploited in targeted attacks. That same day, the US Cybersecurity and Infrastructure Security Administration added it to its catalog of known exploited vulnerabilities and gave federal agencies until Tuesday to patch it.

Despite the severity and the availability of a patch, admins have been slow to fix it, researchers said.