CVE-2021-21551

CVE-2021-21551 is an insufficient access control flaw (CWE-782) in Dell's dbutil_2_3.sys driver, present on Dell systems for roughly 12 years before being patched. A local, authenticated user can trigger the flaw by sending crafted requests (IOCTLs) to the driver, gaining the ability to read and write arbitrary memory. An attacker who exploits it can escalate privileges (typically to kernel/SYSTEM level), cause a denial of service, or disclose information, making it a useful stepping stone for post-compromise attacks. Any Dell machine that shipped or ran the dbutil driver — used in Dell support and BIOS/BIOS-update tooling — is affected, and public reporting indicates hundreds of millions of Dell PCs are exposed. The flaw is actively exploited: it is listed in CISA's Known Exploited Vulnerabilities Catalog (added 2022-03-31), public PoCs exist, and the Lazarus APT reportedly used it in attacks to deploy a rootkit; EPSS puts the 30-day exploitation probability at 79.2%.

What to do: Apply Dell's updated driver/firmware per vendor instructions, as required by CISA's KEV catalog. Inventory your fleet for the dbutil_2_3.sys driver file (commonly found with Dell support tools and BIOS update utilities) and prioritize patching endpoints, since the bug requires only local user access. Hunt for signs of local privilege-escalation activity consistent with public PoCs, given documented Lazarus APT use to deploy a rootkit.