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CVE-2021-25681

7.5 HIGH

📋 TL;DR

CVE-2021-25681 allows attackers to exfiltrate data from vulnerable AdTran Personal Phone Manager servers using DNS tunneling. This affects organizations using AdTran NetVanta 7060 and 7100 appliances with Personal Phone Manager 10.8.1 software. The affected appliances are End of Life and will not receive patches.

💻 Affected Systems

Products:
  • AdTran NetVanta 7060
  • AdTran NetVanta 7100
  • AdTran Personal Phone Manager
Versions: 10.8.1
Operating Systems: Embedded firmware
Default Config Vulnerable: ⚠️ Yes
Notes: Only affects Personal Phone Manager software on specified NetVanta appliances. Appliances are End of Life as of vulnerability disclosure.

📦 What is this software?

Personal Phone Manager by Adtran

View all CVEs affecting Personal Phone Manager →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Sensitive data exfiltration including credentials, call records, and configuration files leading to complete system compromise and lateral movement.

🟠

Likely Case

Data exfiltration from the phone management system including user information, call logs, and potentially credentials.

🟢

If Mitigated

Limited impact with proper network segmentation and DNS filtering preventing data exfiltration.

🌐 Internet-Facing: HIGH - Web servers exposed to internet can be used as DNS redirectors for arbitrary data exfiltration.
🏢 Internal Only: MEDIUM - Internal attackers or compromised systems could still exploit this for data exfiltration within the network.

🎯 Exploit Status

Public PoC: ⚠️ Yes
Weaponized: LIKELY
Unauthenticated Exploit: ⚠️ Yes
Complexity: LOW

Public exploit code available on GitHub and Packet Storm. Exploitation requires network access to the vulnerable web interface.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: None

Vendor Advisory: http://adtran.com

Restart Required: No

Instructions:

No official patch available. Appliances are End of Life. Replace with supported hardware or implement workarounds.

🔧 Temporary Workarounds

Network Segmentation

all

Isolate affected appliances from sensitive networks and restrict outbound DNS traffic.

DNS Filtering

all

Implement DNS filtering to block suspicious DNS queries and prevent data exfiltration.

🧯 If You Can't Patch

  • Decommission affected NetVanta 7060/7100 appliances and replace with supported hardware
  • Implement strict network access controls to limit communication with affected systems

🔍 How to Verify

Check if Vulnerable:

Check if running AdTran Personal Phone Manager 10.8.1 on NetVanta 7060 or 7100 appliances via web interface or console.

Check Version:

Check web interface at http://[device-ip]/ or use console commands specific to AdTran appliances.

Verify Fix Applied:

Test DNS exfiltration attempts using public PoC scripts to confirm vulnerability status.

📡 Detection & Monitoring

Log Indicators:

  • Unusual DNS query patterns from appliance IP
  • Multiple DNS requests to unusual domains
  • DNS queries with encoded/obfuscated data

Network Indicators:

  • DNS traffic from appliance to external domains with encoded subdomains
  • Unusually large DNS queries
  • DNS tunneling patterns

SIEM Query:

source_ip=[appliance_ip] AND protocol=dns AND (query_length>100 OR domain_contains_hex OR subdomain_count>5)

📊 Metadata

CVE ID: CVE-2021-25681
CVSS v3 Score: 7.5 (HIGH)
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Published: April 20, 2021
Last Updated: November 21, 2024

🔗 References

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