Full Report
Lenovo is warning about high-severity BIOS flaws that could allow attackers to potentially bypass Secure Boot in all-in-one desktop PC models that use customized Insyde UEFI (Unified Extensible Firmware Interface). [...]
Analysis Summary
# Vulnerability: Lenovo UEFI Secure Boot Bypass Flaws (SMM Handler Issues)
## CVE Details
- CVE ID: CVE-2025-4424, CVE-2025-4425, CVE-2025-4426
- CVSS Score: 6.0 (Medium) for CVE-2025-4424, 8.2 (High) for CVE-2025-4425, 6.0 (Medium) for CVE-2025-4426
- CWE: Improper Input Validation (CWE TBD, related to SMM handling)
## Affected Systems
- Products: Lenovo IdeaCenter AIO 3 models, Lenovo Yoga AIO models
- Versions: Specific vulnerable versions are not detailed, but users should check Lenovo's advisory for affected machine types/firmware baseline versions.
- Configurations: Affects devices utilizing vulnerable UEFI firmware components, potentially related to the `SetupAutomationSmm` handler.
## Vulnerability Description
Multiple vulnerabilities were discovered in Lenovo UEFI firmware, stemming primarily from flaws within the `SetupAutomationSmm` SMI handler. These flaws bypass Secure Boot mechanisms, allowing unauthorized execution or modification of firmware settings and potentially escalating privileges within the System Management Mode (SMM) environment.
1. **CVE-2025-4424:** Improper input validation in the SMI handler allows unsanitized calls to `SmmSetVariable`, leading to manipulation of firmware settings.
2. **CVE-2025-4425:** A stack buffer overflow in the `SetupAutomationSmm` handler can lead to SMM privilege escalation and arbitrary code execution.
3. **CVE-2025-4426:** A bug in the SMI handler results in the leakage of SMRAM contents, permitting sensitive information disclosure.
## Exploitation
- Status: PoC available (Implied by the nature of discovery and disclosure, though not explicitly stated as exploited in the wild)
- Complexity: Medium (Requires local access or specific low-level execution to trigger SMM handlers)
- Attack Vector: Local (Typically requires executing malicious code within the OS environment to trigger the vulnerable SMI call)
## Impact
- Confidentiality: High (Due to SMRAM content leakage in CVE-2025-4426)
- Integrity: High (Due to firmware setting manipulation in CVE-2025-4424 and arbitrary code execution in CVE-2025-4425)
- Availability: Medium (Firmware corruption could potentially render systems unusable)
## Remediation
### Patches
- **Lenovo IdeaCenter AIO 3:** Firmware update to version **O6BKT1AA**.
- **Lenovo Yoga AIO:** Fixes are planned, with expected release between September 30 and November 30, 2025.
### Workarounds
- No specific workarounds were detailed other than applying patches immediately. Users should ensure Secure Boot remains enabled and be wary of unauthorized firmware modifications.
## Detection
- **Indicators of Compromise:** Unusual changes to UEFI/BIOS settings persistence mechanisms or unexpected execution within SMM.
- **Detection methods and tools:** Monitoring for attempts to unduly interact with sensitive platform variables or SMI handlers. Users should consult vendor advisory for specific machine type detection guidance.
## References
- Vendor Advisory: hxxps://support.lenovo.com/us/en/product_security/LEN-201013
- Binarly Advisory (CVE-2025-4424): hxxps://www.binarly.io/advisories/brly-2025-017
- Binarly Advisory (CVE-2025-4425): hxxps://www.binarly.io/advisories/brly-2025-016
- Binarly Advisory (CVE-2025-4426): hxxps://www.binarly.io/advisories/brly-2025-018