CVE-2025-35991 Overview
CVE-2025-35991 is an improper initialization vulnerability [CWE-665] in the Unified Extensible Firmware Interface (UEFI) firmware for certain Intel platforms operating within Ring 0: Bare Metal OS. The flaw allows a local privileged attacker to disclose sensitive information from uninitialized memory regions. Exploitation requires local access, high attack complexity, and high privileges, with no user interaction. The impact is limited to confidentiality of the vulnerable system, with no integrity or availability consequences. Intel disclosed the issue through Intel Security Advisory SA-01413.
Critical Impact
A local adversary with privileged access may extract sensitive data from UEFI firmware memory, exposing secrets handled at the Ring 0 firmware layer.
Affected Products
- Intel UEFI firmware for affected Intel platforms (see Intel SA-01413)
- Ring 0: Bare Metal OS components running on impacted Intel hardware
- Systems shipping with the vulnerable UEFI firmware versions identified by Intel
Discovery Timeline
- 2026-05-12 - CVE-2025-35991 published to NVD
- 2026-05-13 - Last updated in NVD database
Technical Details for CVE-2025-35991
Vulnerability Analysis
The vulnerability stems from improper initialization within UEFI firmware code paths executing in Ring 0: Bare Metal OS context. Firmware routines fail to fully initialize memory buffers or data structures before they are read or returned to calling code. An attacker with privileged local access can observe residual data left in those uninitialized regions.
Because the firmware runs at the highest processor privilege level, leaked memory may contain secrets, configuration data, or internal firmware state that should remain confined to the platform. The Intel advisory categorizes this as an information disclosure issue affecting confidentiality only, with no direct path to integrity or availability impact.
Exploitation requires meeting specific attack preconditions and chaining privileged execution with the high-complexity steps needed to trigger the uninitialized read. The flaw does not provide code execution on its own but can support broader attack chains by exposing data useful for follow-on exploitation.
Root Cause
The root cause is classified as CWE-665: Improper Initialization. Firmware code paths allocate or reference memory and structures without ensuring all fields are written before use. The result is a read of stale or attacker-relevant data from regions that should have been zeroed or fully populated.
Attack Vector
The attack vector is local. A system software adversary already operating with privileged user rights triggers the vulnerable firmware path during normal interaction with Ring 0 interfaces. No user interaction is required, but the attacker must satisfy specific platform conditions to reach the uninitialized data. The vulnerability manifests in firmware initialization logic and is described in the Intel advisory referenced below. See the Intel Security Advisory SA-01413 for technical details.
Detection Methods for CVE-2025-35991
Indicators of Compromise
- No public indicators of compromise have been published for CVE-2025-35991, and no exploitation in the wild has been reported.
- Unexpected firmware version mismatches between deployed systems and vendor-published baselines may indicate tampering or missing patches.
- Anomalous low-level firmware interface calls from privileged processes warrant review during incident response.
Detection Strategies
- Inventory UEFI firmware versions across the fleet and compare against Intel SA-01413 fixed versions to identify exposed hosts.
- Monitor privileged process activity that interacts with firmware interfaces, SMM handlers, or platform-specific Ring 0 APIs.
- Correlate firmware update events with change-management records to confirm that mitigations were applied through approved channels.
Monitoring Recommendations
- Enable platform attestation and Trusted Platform Module (TPM) measurements to detect firmware integrity changes.
- Log and review administrative actions that load drivers or kernel modules capable of issuing firmware calls.
- Track vendor advisories and OEM firmware bulletins for follow-on updates referencing Intel SA-01413.
How to Mitigate CVE-2025-35991
Immediate Actions Required
- Identify all Intel-based systems running UEFI firmware versions called out in Intel SA-01413 and prioritize them for patching.
- Apply OEM-provided UEFI firmware updates that incorporate Intel's fix as soon as they are validated for the environment.
- Restrict local administrative access on affected platforms to reduce the population of users able to meet the privilege requirement.
Patch Information
Intel has published guidance and fixed firmware references through Intel Security Advisory SA-01413. OEM vendors integrate Intel's reference firmware updates into their own BIOS/UEFI releases, so administrators should obtain updated firmware images from the system manufacturer for each affected platform model.
Workarounds
- Enforce least privilege so that only essential administrators can execute code at the privilege level required to reach the vulnerable firmware path.
- Enable Secure Boot, BIOS administrator passwords, and firmware write protection to limit unauthorized firmware interaction.
- Where firmware updates are not yet available, increase monitoring of privileged sessions and physical access to affected hardware.
# Configuration example: query installed UEFI firmware version on Linux
sudo dmidecode -s bios-version
sudo dmidecode -s bios-release-date
# Verify Secure Boot status
mokutil --sb-state
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
