CVE-2014-7859 – This CVE describes a critical stack-based buffe... (How to Fix)

Q: What is the severity of CVE-2014-7859?

CVE-2014-7859 has a CVSS score of 9.8 (CRITICAL). This CVE describes a critical stack-based buffer overflow vulnerability in D-Link network storage device firmware. Remote attackers can execute arbitrary code by sending specially crafted HTTP requests with malicious Host and Referer headers. Affected devices include D-Link DNR and DNS series network storage products running vulnerable firmware versions.

📋 TL;DR

This CVE describes a critical stack-based buffer overflow vulnerability in D-Link network storage device firmware. Remote attackers can execute arbitrary code by sending specially crafted HTTP requests with malicious Host and Referer headers. Affected devices include D-Link DNR and DNS series network storage products running vulnerable firmware versions.

💻 Affected Systems

Products:

D-Link DNR-320L
D-Link DNS-320LW
D-Link DNR-322L
D-Link DNR-326
D-Link DNS-327L

Versions: DNR-320L and DNS-320LW before 1.04b08, DNR-322L before 2.10 build 03, DNR-326 before 2.10 build 03, DNS-327L before 1.04b01

Operating Systems: Embedded Linux firmware

Default Config Vulnerable: ⚠️ Yes

Notes: Affects the login_mgr.cgi component which handles authentication. No authentication required for exploitation.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete device compromise leading to remote code execution, data theft, device takeover, and potential lateral movement to other network systems.

🟠

Likely Case

Remote attacker gains shell access to the device, installs malware, creates persistent backdoors, and uses the device as a pivot point for further attacks.

🟢

If Mitigated

Attack attempts are blocked at network perimeter, devices are isolated, and monitoring detects exploitation attempts.

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: CONFIRMED

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Public exploit code available since 2015. Exploitation requires sending HTTP requests with crafted headers to the vulnerable CGI endpoint.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: DNR-320L/DNS-320LW: 1.04b08+, DNR-322L/DNR-326: 2.10 build 03+, DNS-327L: 1.04b01+

Vendor Advisory: http://www.search-lab.hu/media/D-Link_Security_advisory_3_0_public.pdf

Restart Required: Yes

Instructions:

1. Download latest firmware from D-Link support site. 2. Log into device web interface. 3. Navigate to System > Firmware Update. 4. Upload and install new firmware. 5. Device will reboot automatically.

🔧 Temporary Workarounds

Network Access Control

linux

Block external access to affected devices using firewall rules

iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP

Web Application Firewall

all

Deploy WAF to filter malicious HTTP headers

ModSecurity rules to detect and block Host/Referer header overflow attempts

🧯 If You Can't Patch

Isolate affected devices in separate VLAN with strict access controls
Implement network monitoring for exploitation attempts and disable web interface if not required

🔍 How to Verify

Check if Vulnerable:

Check firmware version in device web interface under System > Firmware Information

Check Version:

curl -s http://device-ip/fw_version.cgi | grep Firmware

Verify Fix Applied:

Confirm firmware version matches or exceeds patched versions listed above

📡 Detection & Monitoring

Log Indicators:

HTTP requests with unusually long Host/Referer headers
Multiple failed login attempts from login_mgr.cgi
Device reboot logs after exploitation

Network Indicators:

HTTP POST requests to /login_mgr.cgi with oversized headers
Unusual outbound connections from NAS devices
Shell command execution patterns in HTTP traffic

SIEM Query:

source="firewall" dest_port=80 OR dest_port=443 (http_user_agent="*login_mgr.cgi*" AND (http_host_length>100 OR http_referer_length>100))

📊 Metadata

CVE ID: CVE-2014-7859

CVSS v3 Score: 9.8 (CRITICAL)

CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-119

Published: August 25, 2017

Last Updated: April 20, 2025

🔗 References

http://packetstormsecurity.com/files/132075/D-Link-Bypass-Buffer-Overflow.html Third Party Advisory,VDB Entry
http://seclists.org/fulldisclosure/2015/May/125 Mailing List,Third Party Advisory,VDB Entry
http://www.search-lab.hu/media/D-Link_Security_advisory_3_0_public.pdf Technical Description,Third Party Advisory
http://www.securityfocus.com/archive/1/535626/100/200/threaded Third Party Advisory,VDB Entry
http://www.securityfocus.com/bid/74878 Third Party Advisory,VDB Entry
http://packetstormsecurity.com/files/132075/D-Link-Bypass-Buffer-Overflow.html Third Party Advisory,VDB Entry
http://seclists.org/fulldisclosure/2015/May/125 Mailing List,Third Party Advisory,VDB Entry
http://www.search-lab.hu/media/D-Link_Security_advisory_3_0_public.pdf Technical Description,Third Party Advisory
http://www.securityfocus.com/archive/1/535626/100/200/threaded Third Party Advisory,VDB Entry
http://www.securityfocus.com/bid/74878 Third Party Advisory,VDB Entry

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