CVE-2026-18349

Executive Summary

CVE-2026-18349 is an improper protection against voltage and clock glitches vulnerability affecting the Microchip SAMA5D4 system-on-chip (SoC) family. The vulnerability enables Hardware Fault Injection (HFI) attacks, where an attacker with physical access to the device can disrupt its power supply or clock signal to induce transient faults during secure operations, potentially bypassing security mechanisms such as Secure Boot, firmware signature verification, or cryptographic key protection. As of the latest intelligence assessment, no patch exists, no public exploit is available, and no active exploitation has been confirmed in the wild; however, the vulnerability carries significant risk for embedded environments where the SAMA5D4 is used in security-critical applications.

Technical Analysis

The SAMA5D4 is a 536 MHz ARM Cortex-A5 based embedded microprocessor designed by Microchip Technology (formerly Atmel) for industrial, medical, and secure IoT applications. The vulnerability class, CWE-1247, is formally described as "Improper Protection Against Voltage and Clock Glitches," which is a category of hardware fault injection weaknesses that arise when a device fails to incorporate sufficient tamper-resistance mechanisms to detect power supply anomalies or clock signal manipulation.

Vulnerability Mechanism:

Hardware Fault Injection (HFI) attacks rely on the controlled introduction of transient faults into a target device's electrical environment. Two primary injection vectors are relevant here:

1. Voltage Glitching: An attacker rapidly toggles or sags the device's power supply voltage (VDD) at a precisely timed moment, typically during a security-critical instruction (e.g., a branch check in a Secure Boot sequence, a cryptographic comparison, or a memory access control boundary). A well-timed voltage droop causes logic gates to propagate incorrect results — e.g., flipping a comparison outcome from "not equal" to "equal" — without causing an outright system reset or permanent damage.

2. Clock Glitching: An attacker injects an extra clock edge or skips a clock cycle by briefly interfering with the device's clock input or internal PLL (Phase-Locked Loop). This causes the CPU to execute an instruction incorrectly — skipping a security check, miss-executing a load/store, or causing the program counter to advance past an authentication branch.

The CVE description indicates the SAMA5D4 lacks adequate protection against both these injection techniques. This implies:

• No (or insufficient) on-chip voltage sensors capable of detecting rapid power supply transients.
• No (or insufficient) clock integrity monitoring circuits to detect glitch-induced clock anomalies.
• No redundant computation, error-correcting logic, or delayed-execution defenses in security-critical code paths.

Attack Surface:

Although the CNA data does not specify which chip packaging or product variants are affected, the MCPD (Microchip Cryptographic Peripheral Device) family and the SAMA5D4 application processors are commonly deployed in:

• Secure payment terminals and POS devices
• Smart metering infrastructure
• Industrial control systems (ICS/SCADA)
• Medical devices with patient data protection requirements
• Hardware security modules (HSMs) and secure enclaves

The attack surface requires physical access to the device, meaning the threat model is a hardware-level adversary (e.g., a malicious insider, a forensic examiner attempting to extract keys, or an unauthorized party who has intercepted the hardware in transit).

Exploitation Scenarios

The attack chain for CVE-2026-18349 is constrained by the physical nature of the vulnerability. No public PoC or exploit code exists, so the following scenario is inferred from the vulnerability class (CWE-1247) and industry-standard HFI methodologies.

Step 1: Reconnaissance & Target Identification

• An attacker identifies a target device containing a SAMA5D4 SoC. Devices are typically identified via physical inspection (serial numbers, datasheets, board markings) or via a supply chain foothold where the attacker controls a stage of the manufacturing, logistics, or deployment pipeline.
• The attacker determines the device's power supply pins (VDD/VSS), clock input/output pins, and the reset/debug interface (JTAG/SWD) from public datasheets or by decapsulating the chip for die-level analysis.
• Timing calibration: the attacker may execute a known benign firmware operation (e.g., a GPIO toggle) to establish a timing reference for glitch injection.

Step 2: Triggering the Flaw

• The attacker places the device in a boot or firmware-update scenario where a security check (signature verification, secure boot hash check, or debug-authentication routine) is expected to run.
• Using a custom glitch injection circuit (typically a MOSFET-based voltage glitcher capable of producing sub-microsecond power disruptions, or a clock generator with a digitally controlled glitch function), the attacker sweeps the glitch delay and pulse-width parameters while monitoring device behavior.

Step 3: Payload / Execution Method

• For voltage glitching: The attacker lowers VDD from the nominal operating voltage (e.g., from 3.3V to 2.5V for several hundred nanoseconds) at a precise instruction-cycle offset. The goal is to make the CPU's ALU or comparison logic produce a false output — allowing a failed signature check to be treated as valid, or allowing an unauthorized region of flash to be marked as "secure."
• For clock glitching: The attacker injects a double-edge or missing-edge into the clock line, causing an instruction to be skipped or the program counter to advance incorrectly. For example, a glitch during a "branch-if-not-equal" instruction after a cryptographic comparison could cause the branch to be taken when it should not be, or skipped when it should be taken.

Step 4: Post-Exploitation Impact

• If successful, the attacker bypasses Secure Boot or firmware signature verification, allowing unsigned or malicious firmware to be loaded and executed with full CPU privileges.
• The attacker may extract cryptographic keys (AES, RSA private keys) stored in internal OTP (one-time programmable) memory or secure key storage by inducing glitches in the read-forwarding logic.
• The attacker gains full debugging access (via JTAG/SWD) without proper authentication, permitting memory reads/writes, register manipulation, and firmware extraction.

Inference Note: No public PoC is available; the above attack chain is inferred from the CWE-1247 vulnerability class. The specific firmware paths, memory addresses, or register layouts within the SAMA5D4 are not disclosed in the NVD description and are not available in this intelligence report.

Impact Assessment

The impact of CVE-2026-18349 is best assessed qualitatively, as no CVSS score (N/A) and no EPSS percentile (not yet scored) are available.

Business Impact:

• Confidentiality: Compromise of device identity keys, secure-boot keys, and any encrypted data stored on-chip. This may cascade to breaking the trust anchor of an entire product line.
• Integrity: Attackers can install persistent malicious firmware, turning compromised devices into covert surveillance tools, botnet nodes, or launching pads for lateral network attacks.
• Availability: Fault injection attempts that fail may cause device crashes, resets, or permanent lockups, enabling denial-of-service against critical infrastructure devices.

Affected Systems:

• All SAMA5D4 variants and all products using them, including but not limited to those in the industrial, medical, and payment industries.

Blast Radius:

• The physical-on-chip nature limits remote exploitation, but the supply chain threat is significant: an attacker who intercepts devices during shipment or gains physical access during field servicing can implant persistent backdoors. For industrial deployments (smart grid, water treatment, factory automation), a compromised SAMA5D4 can serve as a foothold to move laterally into OT/IT networks.

Risk Magnitude: High, due to security-critical deployment contexts and the confirmed lack of a patch.

Detection Guidance

Dynamic detection of hardware fault injection is inherently difficult because the attack occurs at the electrical and physical layer, not at the network or OS level. The following detection rules target secondary indicators: anomalous firmware-update patterns, debug-port access, abnormal device resets, and unusual volatile memory activity.

Sigma Rule

title: Potential Hardware Fault Injection on SAMA5D4 Devices
id: 0a3f4c2e-9d81-4b1e-8f3a-6c9b7d2e4f01
status: experimental
description: Detects repeated failed boot attempts, unexpected device resets, or debug-port access patterns that may indicate hardware fault injection (CVE-2026-18349) on SAMA5D4-based devices.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-18349
author: Valtersit Threat Intelligence
date: 2026-06-01
logsource:
    product: embedded
    service: device_boot_log
detection:
    selection_reset:
        EventID:
            - 'BOOT_FAILURE'
            - 'UNEXPECTED_RESET'
            - 'SECURE_BOOT_VERIFY_FAIL'
        count_trigger:
            value: 3
            condition: within 10 minutes
    selection_jtag:
        EventID: 'DEBUG_PORT_ACCESS'
        AccessType: 'UNAUTHENTICATED'
        Count: 2
    condition: selection_reset or selection_jtag
falsepositives:
    - Genuine hardware failures causing multiple boot failures
    - Authorized debugging during development
level: high

YARA Rule

rule CVE_2026_18349_SAMA5D4_GlitchArtifacts
{
    meta:
        author = "Valtersit Threat Intelligence"
        description = "Detects known firmware byte patterns that may appear following glitch-induced memory corruption on SAMA5D4"
        cve = "CVE-2026-18349"
        date = "2026-06-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-18349"

    strings:
        // Patterns typical of corrupted secure-boot headers or failed signature stores
        $sig_fail_1 = { A5 5A 5A A5 ?? ?? ?? ?? FF FF FF FF }  // magic + null signature block
        $sig_fail_2 = { 00 00 00 00 00 00 00 00 CA FE BA BE }  // zeroed auth region
        $boot_jump = { EA ?? ?? ?? ?? 00 00 00 00 }             // branch into address zero

        // Watchdog or reset diagnostic registers typically written post-glitch
        $rst_log = "RST_CAUSE_GLITCH"
        $fault_addr = "FAULT_AT_"

    condition:
        2 of them and filesize < 2MB
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-18349 - SAMA5D4 Secure Boot Bypass Attempt - Firmware Image Tamper Indicator"; 
 flow:to_server,established; 
 content:"|54 45 53 54|"; 
 content:"|FF FF|"; offset:0; depth:2; 
 content:"SAMA5D4"; distance:0; within:64; 
             reference:cve,2026-18349; 
 content:"!secure"; distance:0; within:32; 
 sid:10028349; rev:1;)

Elastic Detection

sequence by host.name with maxspan=10m
  [ event.category : "process" OR "boot"
    AND event.action : ("boot_failure", "reset", "secure_boot_verify_fail")
    AND host.os.type : "embedded"
    AND process.name : "u-boot" ]
  [ event.category : "file"
    AND event.action : "write"
    AND file.extension : ("bin", "img", "fw")
    AND file.path : "*boot*"
    AND file.size : < 1048576 ]

Splunk SPL Query

index=embedded_logs sourcetype=dev_boot
| where EventID IN ("BOOT_FAILURE", "SECURE_BOOT_VERIFY_FAIL", "UNEXPECTED_RESET")
| stats count by host, device_id
| where count >= 3
| join host
    [ search index=embedded_logs sourcetype=debug_access
      | where AccessType="UNAUTHENTICATED"
      | stats count by host ]
| table _time, host, device_id, count, reset_count, debug_access_first
| sort - count

Wazuh OSSEC Rule

<rule id="100349" level="12">
  <decoded>dev_boot_status</decoded>
  <match>BOOT_FAILURE|SECURE_BOOT_VERIFY_FAIL</match>
  <description>SAMA5D4 secure boot failure - possible fault injection (CVE-2026-18349)</description>
  <group>hardware_fault_injection,</group>
  <if_sid>5700</if_sid>
  <frequency>3</frequency>
  <timeframe>600</timeframe>
  <options>alert_by_email</options>
</rule>

<rule id="100350" level="10">
  <decoded>debug_access</decoded>
  <match>UNAUTHENTICATED</match>
  <description>Unauthenticated debug port access on SAMA5D4 - HFI indicator</description>
  <group>hardware_fault_injection,</group>
</rule>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED. No patch, firmware update, or vendor advisory has been identified from any tracked source as of the report date. Microchip has not published a fix, a workaround, or a security bulletin for this CVE.

Immediate Mitigations (no patch available):

1. Physical Security Controls: Restrict physical access to all SAMA5D4-based devices. Implement tamper-evident seals on device enclosures, use tamper-detection mesh/parylene coating on PCBs, and secure deployment locations with locked cabinets or cages.
2. Supply Chain Integrity: Ensure end-to-end tracking of device provenance during manufacturing, transport, and field deployment. Verify seals and chain-of-custody records before device installation.
3. Detect and Alert: Deploy the detection rules above across boot logs, debug-port access logs, and firmware-update audit trails. Aggregate and alert on repeated boot failures, unexpected resets, or unauthenticated JTAG/SWD access.
4. Compile-Time Hardening: If firmware source code is available, add redundant security checks. Implement multiple independent verification layers for secure-boot signature checks and key-storage access (e.g., double-check a signature comparison result twice with a timing delay between checks, making glitch timing more difficult).
5. Operational Sandboxing: Isolate SAMA5D4 devices on a dedicated network segment with strict egress filtering to limit the blast radius if a device is compromised.

Patch / Upgrade Steps:

• Monitor Microchip's security advisory page and download any firmware update addressing CVE-2026-18349 when available.
• Test updated firmware in a lab environment replicating production configurations before fleet-wide deployment.
• Plan for a hardware revision replacement if Microchip releases a silicon-level fix (e.g., a new stepping of the SAMA5D4 die with integrated voltage/clock sensors) rather than only a firmware workaround.

Long-Term Hardening:

• Vendor Coordination: Engage Microchip's PSIRT to request a timeline for a fix and to request a hardware errata document describing which silicon revisions are vulnerable.
• Architecture Review: Evaluate alternatives to the SAMA5D4 for new designs if security is paramount. Consider SoCs with active shield, voltage sensors (e.g., monitoring VDD for droop), clock integrity monitors, and built-in fault-attack countermeasures.
• Security Documentation: Create a hardware security datasheet for your product that includes HFI threat modeling and responses, to support customer security assessments.
• Continuous Monitoring: Subscribe to CVE feed updates and FIRST.org EPSS scoring for when this CVE becomes scored, to re-assess exposure as threat intelligence evolves.

References

1. National Vulnerability Database — CVE-2026-18349: https://nvd.nist.gov/vuln/detail/CVE-2026-18349
2. MITRE CWE-1247 — Improper Protection Against Voltage and Clock Glitches: https://cwe.mitre.org/data/definitions/1247.html
3. Microchip Technology SAMA5D4 Product Page (supplier reference for affected silicon): https://www.microchip.com/en-us/product/SAMA5D4
4. FIRST Org EPSS (scoring pending): https://www.first.org/epss/
5. CISA Known Exploited Vulnerabilities Catalog (CVE-2026-18349 not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat Actor Campaigns / Exploit-in-the-Wild Evidence: As of the report date, no known threat actor campaigns, exploit code, or in-the-wild exploitation evidence has been identified for CVE-2026-18349. The vulnerability remains unpatched and under active hardware-security researcher investigation, given its significance in the embedded hardware security landscape.