CVE-2026-35075: Hardcoded Default Password in Firmware Enables Full Device Takeover (CVSS 9.8)

CVE-2026-35075: Hardcoded Default Password in Firmware Image

A critical hardcoded credential vulnerability tracked as CVE-2026-35075 has been disclosed affecting embedded devices with a hardcoded default password embedded in their firmware. With a CVSS v3.1 score of 9.8 (Critical), an unauthenticated remote attacker can extract this password by downloading and analyzing the firmware image — then use it to gain full administrative access to all affected devices with zero exploitation complexity.

The vulnerability was published to the NIST NVD on June 3, 2026 and follows the well-documented CWE-259 (Use of Hard-coded Password) pattern, one of the most persistent and dangerous vulnerability classes in embedded and IoT device firmware.

Vulnerability Overview

Technical Details

Root Cause: CWE-259 Hardcoded Password

CWE-259 describes firmware or software where a password is compiled directly into the binary rather than being generated, configured, or randomly assigned at deployment time. Hardcoded passwords in firmware are a persistent vulnerability class because:

1. The password is identical across all deployed units — one extracted password compromises every device running the same firmware version
2. Firmware images are often publicly downloadable — vendors publish firmware for customer update purposes, making extraction trivial
3. Static analysis tools readily extract strings — even without advanced reverse engineering, basic strings or binwalk analysis can reveal credentials

Extraction and Exploitation Path

Attacker downloads firmware image from vendor website (or intercepts update)
  → Analyzes firmware with binwalk / strings / Ghidra / IDA Pro
    → Extracts hardcoded password from binary, configuration file, or script
      → Authenticates to any affected device using extracted credential
        → Full administrative access granted
          → Configuration modification, data exfiltration, backdoor installation

Basic firmware extraction example:

# Download firmware image
wget https://vendor.example.com/firmware/device-v4.0.bin
 
# Extract and identify credential strings
binwalk -e device-v4.0.bin
strings device-v4.0.bin | grep -iE '(password|passwd|secret|admin|root|default)'
 
# Common results:
# admin:manufacturer_default_2024!
# root:SuperSecretFactoryPassword

The CVSS score of 9.8 reflects:

• Attack Vector: Network — device accessible remotely
• Attack Complexity: Low — password extraction requires no specialized skill
• Authentication: None — the hardcoded credential bypasses authentication entirely
• All three impact dimensions: High (full device control)

Why Hardcoded Passwords Persist in Firmware

Despite being a well-documented vulnerability class since at least the 2000s, hardcoded passwords persist in embedded device firmware due to:

Impact Assessment

Hardcoded default password vulnerabilities have powered some of the most damaging mass-exploitation events in recent history, including the Mirai botnet (2016), which leveraged default credentials across millions of IoT devices to launch record-breaking DDoS attacks exceeding 1 Tbps.

Affected Systems

The NVD description confirms this affects all devices running the vulnerable firmware version. Organizations should:

1. Identify all devices from the affected vendor in their environment
2. Check device firmware versions against the vendor security advisory
3. Assume all units with the vulnerable firmware are compromised if exploitation cannot be ruled out

Contact the affected vendor's security team and monitor their official security advisory channel for:

• Precise model numbers and firmware version ranges
• Availability of patched firmware
• Vendor-recommended mitigations

Remediation

Immediate Actions

1. Apply firmware updates — Install patched firmware from the vendor that removes or replaces the hardcoded default password. Monitor the vendor's security advisory page for the specific update:

   # Verify firmware version before and after update
   # Use vendor-specific CLI or web interface
   show version
   # or
   cat /etc/firmware_version

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2. Change default credentials immediately — Even on unpatched devices, access the management interface and change all default passwords to strong, unique values. While this does not fix the underlying hardcoded credential (which may still be accessible via firmware extraction), it reduces immediate exploitation risk.

3. Restrict management interface access — Firewall the device management interface to authorized management hosts only:

   # Allow only management VLAN to reach device admin ports
   iptables -A INPUT -p tcp --dport 22 -s <mgmt-subnet> -j ACCEPT
   iptables -A INPUT -p tcp --dport 22 -j DROP
   iptables -A INPUT -p tcp --dport 80 -s <mgmt-subnet> -j ACCEPT
   iptables -A INPUT -p tcp --dport 80 -j DROP
   

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4. Scan for internet exposure — Use Shodan or Censys to identify whether affected devices are internet-accessible:

   # Check Shodan for exposed device management interfaces
   shodan search "vendor:AffectedManufacturer port:80,22,443" --fields ip_str,port,org

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5. Monitor for unauthorized access — Review authentication logs on affected devices for access using the default credential string, which may indicate prior compromise.

6. Incident response — If exploitation cannot be ruled out, treat affected devices as compromised and:

   • Isolate from the network
   • Collect forensic artifacts (log files, network captures)
   • Reimage with patched firmware from a trusted source
   • Rotate all credentials the device had access to

Defense-in-Depth for Embedded Devices

Priority 1: Apply vendor firmware patch immediately upon availability
Priority 2: Change all default credentials to unique strong passwords
Priority 3: Network isolation — management interfaces must not be internet-accessible
Priority 4: Asset inventory — maintain a current list of all embedded devices and firmware versions
Priority 5: Network monitoring — alert on authentication attempts using known default credentials
Priority 6: Firmware signing verification — ensure only vendor-signed firmware is installable

Hardcoded Credentials in Historical Context

CWE-259 hardcoded password vulnerabilities represent one of the most consistently exploited vulnerability classes across embedded and IoT device history:

The OWASP IoT Top 10 consistently lists hardcoded credentials as the #1 or #2 vulnerability in IoT device security, and CISA's ICS security advisories frequently flag this issue in operational technology device firmware.

Key Takeaways

1. CVE-2026-35075 is a CVSS 9.8 critical hardcoded default password vulnerability affecting all units running the vulnerable firmware version — no exploitation skill required
2. The password is extractable from the publicly available firmware image using basic analysis tools, meaning mass exploitation is trivially achievable
3. Every device running the vulnerable firmware is equally at risk — there is no per-device variation in the hardcoded credential
4. Immediate mitigations: change default passwords, isolate management interfaces, and apply vendor firmware patches when available
5. Contact the affected vendor directly and monitor their security advisory channel for patched firmware release dates

Sources

• CVE-2026-35075 — NIST NVD
• CWE-259: Use of Hard-coded Password
• CISA ICS-CERT Advisories
• OWASP IoT Top 10
• NIST SP 800-213: IoT Device Cybersecurity Guidance