| Title | Author | Created | Published | Tags | | ------------------------------ | ---------- | --------------- | --------------- | ---------------------------- | | Exploiting UEFI - Gigabyte MBs | Jon Marien | August 29, 2025 | August 29, 2025 | [[#issessions\|#issessions]] | # Slide outline ## Slide 1 — Why UEFI Security Matters UEFI runs at boot with the highest privileges, controls Secure Boot, and is largely invisible to OS-level tools, making it a prime persistence layer for attackers. Compromise here can survive OS reinstalls and bypass higher-layer defenses, so firmware hygiene is critical. ## Slide 2 — What is UEFI? UEFI is the standardized firmware interface that initializes hardware and launches the OS, replacing legacy BIOS. It provides a pre-boot environment where drivers and security policies run before the kernel. ## Slide 3 — UEFI vs. BIOS UEFI offers modular drivers, richer pre-boot services, and security features like Secure Boot and measured boot beyond legacy BIOS capabilities. These features expand functionality but also enlarge the pre-OS attack surface. ## Slide 4 — UEFI Boot Process (SEC → PEI → DXE → BDS → RT) Early phases initialize CPU/chipset and memory, then dispatch DXE drivers, enforce boot policy, and hand off to the OS with runtime services. Attackers often target DXE or runtime interfaces to gain pre-OS execution. ## Slide 5 — Security Features Secure Boot, measured boot, TPM in tegration, and signed firmware aim to ensure only trusted code runs pre-OS. SMM protections, if properly configured, help isolate critical handlers and memory. ## Slide 6 — CPU Rings and Privilege Ring 3 apps → Ring 0 kernel → Ring -1 hypervisor → Ring -2 SMM, with lower numbers meaning higher privilege. SMM operates beyond OS visibility and controls hardware directly, so exploits here can bypass all higher layers. ## Slide 7 — Rootkits and Bootkits Firmware bootkits load before the OS, evade antivirus, and persist across reinstalls, enabling full hardware and memory control. Persistence often abuses UEFI variables, DXE drivers, SPI flash, or SMM handler flaws. ## Slide 8 — SMM Security SMM is a privileged mode for system management with exclusive SMRAM; vulnerable SMI handlers enable undetectable, powerful persistence. Arbitrary code execution in SMM undermines Secure Boot and OS integrity, often requiring firmware reflash to recover. ## Slide 9 — Vulnerability Overview (Updated to BRLY-2025-009/CVE-2025-7027) Binarly disclosed CVE-2025-7027 in Gigabyte UEFI: an SMM handler issue that permits controlled writes in SMRAM via attacker-influenced pointers/variables. Exploitation enables Ring -2 code execution, bypass of SPI flash protections, and installation of persistent firmware implants. ## Slide 10 — Attack Scenario A local attacker with OS-level privileges can trigger SMI paths that misuse RBX/RCX state and unvalidated NVRAM variable data to write into SMRAM. Post-exploitation, malware can tamper with flash operations and survive reinstalls, defeating OS-layer defenses. ## Slide 11 — Impact Enables pre-OS persistence, Secure Boot bypass, and stealthy control over the platform below kernel and hypervisor. Traditional EDR can’t reliably see SMM-level implants; remediation may require vendor firmware updates or board reflash. ## Slide 12 — Detection & Mitigation Update firmware from the vendor; follow Gigabyte’s security advisories and apply fixed BIOS releases. Use Secure Boot, restrict physical/admin access, and consider tools like Binarly’s analysis, CHIPSEC, and fwupd-based workflows. ## Slide 13 — Broader Implications Cross-vendor SMM/UEFI flaws and supply-chain risks show why attestation and stronger isolation are rising priorities. Industry direction includes SMM hardening, hardware-backed protections, and standardized firmware security practices. ## Slide 14 — Q&A and Resources Reference the Binarly BRLY-2025-009 advisory and the Low Level explainer video for technical and conceptual context. Point to assessment tools and vendor security portals for checking affected models and obtaining updates. ---- # Presentation script **Opening Hook (0:00–0:30)** “Have you ever considered that the most powerful code on a PC runs before the OS even wakes up, and that if it’s compromised, it can outlive every reinstall and bypass most defenses?” “Tonight is about that layer—UEFI and SMM—and a recent vulnerability that shows how attackers can seize control below the kernel and stay there.” **What UEFI Is (0:31–1:00)** “UEFI is the modern firmware interface that initializes hardware and starts the OS, replacing legacy BIOS with a richer, modular pre-boot environment.” “It’s powerful by design—drivers and policies load before the kernel—so any flaw here can become a stealthy foothold for attackers.” **Why Privilege Rings Matter (1:01–1:30)** “Computers enforce privilege with rings: apps in Ring 3, the OS kernel in Ring 0, hypervisors at Ring -1, and System Management Mode (SMM) at Ring -2.” “SMM is invisible to the OS and has direct hardware access, which means code that lands there can evade normal security controls.” **Rootkits vs. Bootkits (1:31–2:00)** “Rootkits live in the OS, but bootkits and firmware implants load before it, often surviving wipes by hiding in UEFI variables, DXE drivers, or SPI flash.” “This is why pre-OS malware remains so dangerous: it runs first, can tamper with later boot stages, and stays undetected by typical endpoint tools.” **The Vulnerability We’re Covering (2:01–2:45)** “Binarly’s BRLY-2025-009 details CVE-2025-7027 in Gigabyte UEFI firmware, where an SMM handler allows attacker-influenced writes into SMRAM.” “Exploitation elevates from Ring 0 into Ring -2, bypasses SMM flash protections, and enables persistent firmware implants that survive OS reinstalls.” **How The Exploit Path Works (2:46–3:30)** “From an OS context with sufficient rights, an attacker triggers a software SMI and abuses unvalidated state—like RBX/RCX registers and an NVRAM variable—to write controllable data to controllable addresses in SMRAM.” “Once code runs in SMM, it can manipulate flash read/write paths, neutralize Secure Boot checks, and install backdoors that persist across reimages.” **Why This Is Hard To Detect (3:31–4:00)** “SMM lives outside the OS, so EDR and kernel-based defenses can’t reliably observe or intercept SMM handlers or SMRAM content.” “After compromise, even trusted measurements can be subverted, which is why remediation often hinges on clean firmware updates or full reflashing.” **Real-World Stakes (4:01–4:45)** “Pre-OS implants can keylog, exfiltrate secrets, and quietly alter the OS as it boots, effectively controlling the platform under the radar.” “Because the implant executes first, it can blind security tooling and reestablish control no matter how many times the OS is reinstalled.” **What To Do Right Now (4:46–5:30)** “First, apply the vendor’s latest firmware updates—Binarly’s disclosure coincided with Gigabyte updates and CERT guidance to check affected models and patch.” “Enable Secure Boot, restrict physical and administrative access, and consider periodic firmware integrity checks and attestation in higher-assurance environments.” **Tools For Assessment (5:31–6:00)** “Use platform analysis tools to spot risky SMM patterns or modifications—commercial analyzers like Binarly’s platform and open-source frameworks such as CHIPSEC can help.” “For Linux fleets, fwupd-based workflows support distributing firmware updates while performing basic security checks in the process.” **Big Picture (6:01–6:30)** “This class of flaws appears across vendors and supply chains, pushing the industry toward stronger SMM isolation, standard secure development practices, and improved attestation.” “Pre-OS security is no longer niche—it’s a baseline requirement for defending modern systems.” **Closing (6:31–7:00)** “Firmware is part of the security perimeter, and keeping it healthy matters as much as patching the OS and apps.” “For technical details and a clear conceptual explainer, see the Binarly advisory and the Low Level video referenced here.”