Dell BIOS Flaw Lets Attackers Extract Plaintext Passwords Without Brute Force

A Dell BIOS password-storage flaw (CVE-2026-40639) in the DVAR configuration store and SystemPwSmm driver stores passwords using a weak repeating-key XOR scheme that leaks key bytes via null-byte padding, enabling attackers with physical access or SPI flash dumps to recover BIOS passwords quickly. MDSec validated the issue on several Latitude, XPS and Wyse systems; Dell has issued updates for affected models. Attackers could recover passwords, change boot settings, disable Secure Boot, or boot external media; mitigations include applying firmware updates, avoiding password reuse, and enforcing layered physical and firmware protections.