CVE-2020-11899: Treck TCP/IP Buffer Overflow Vulnerability

CVE-2020-11899 Overview

CVE-2020-11899 is an out-of-bounds read vulnerability affecting the Treck TCP/IP stack before version 6.0.1.66. This vulnerability, which is part of the Ripple20 family of vulnerabilities, occurs during IPv6 packet processing and can allow attackers on an adjacent network to read memory beyond intended boundaries, potentially leading to information disclosure or denial of service conditions.

Critical Impact

This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. The Treck TCP/IP stack is embedded in millions of IoT devices, industrial control systems, and enterprise equipment, making this vulnerability particularly widespread.

Affected Products

• Treck TCP/IP stack (versions prior to 6.0.1.66)
• Dell Wyse 5050 All-in-One (including firmware)
• Dell Wyse 7030 (including firmware)
• Dell Wyse 5030 (including firmware)

Discovery Timeline

• 2020-06-17 - CVE-2020-11899 published to NVD
• 2025-11-07 - Last updated in NVD database

Technical Details for CVE-2020-11899

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-bounds Read), a memory corruption flaw that occurs when software reads data past the end of the intended buffer. In the context of the Treck TCP/IP stack, this issue manifests during the processing of IPv6 network packets.

The Treck TCP/IP stack is a lightweight, embedded networking stack used extensively in IoT devices, industrial control systems, medical devices, printers, routers, and enterprise equipment. Its widespread deployment across multiple vendors and industries amplifies the impact of this vulnerability significantly.

As part of the Ripple20 vulnerability set discovered by JSOF, this out-of-bounds read can be exploited by attackers with adjacent network access without requiring authentication or user interaction. The vulnerability can potentially leak sensitive memory contents or cause system instability.

Root Cause

The root cause lies in improper bounds checking during IPv6 packet parsing within the Treck TCP/IP stack. When processing malformed or specially crafted IPv6 packets, the stack fails to properly validate buffer boundaries, allowing read operations to access memory beyond the allocated buffer space. This is a classic input validation error where packet length or offset fields are not adequately verified before being used to access memory.

Attack Vector

An attacker positioned on an adjacent network can exploit this vulnerability by sending specially crafted IPv6 packets to a vulnerable device. The attack requires network adjacency but does not require any authentication credentials or user interaction.

The exploitation process involves:

1. Identifying a target device running a vulnerable version of the Treck TCP/IP stack
2. Crafting malicious IPv6 packets with manipulated header fields or extension headers designed to trigger the out-of-bounds read condition
3. Sending these packets to the target device
4. The vulnerable parsing code reads beyond buffer boundaries, potentially disclosing memory contents or causing service disruption

For detailed technical analysis of this vulnerability and its exploitation mechanics, see the JSOF Ripple20 Overview and the CERT Vulnerability Advisory.

Detection Methods for CVE-2020-11899

Indicators of Compromise

• Unusual IPv6 traffic patterns or malformed IPv6 packets on the network
• Unexpected device crashes, reboots, or stability issues in embedded systems
• Memory access violations or segmentation faults logged by monitoring systems
• Anomalous network behavior from IoT devices, thin clients, or embedded systems

Detection Strategies

• Deploy network intrusion detection systems (IDS) with signatures for Ripple20 vulnerabilities
• Monitor for malformed IPv6 packets, particularly those with unusual extension header configurations
• Implement deep packet inspection for IPv6 traffic targeting embedded devices
• Use asset inventory tools to identify devices running Treck TCP/IP stack versions prior to 6.0.1.66

Monitoring Recommendations

• Enable verbose logging on network boundary devices to capture IPv6 traffic anomalies
• Implement network segmentation to isolate IoT and embedded devices from critical infrastructure
• Monitor vendor security advisories from Cisco, Dell, Intel, and NetApp for product-specific guidance
• Utilize the CISA KEV Catalog to track active exploitation status

How to Mitigate CVE-2020-11899

Immediate Actions Required

• Update the Treck TCP/IP stack to version 6.0.1.66 or later across all affected systems
• Apply vendor-specific firmware updates for Dell Wyse thin clients and other affected products
• Implement network segmentation to limit adjacent network exposure for vulnerable devices
• Disable IPv6 on devices where it is not required and the vulnerability cannot be immediately patched
• Review and restrict network access to embedded systems and IoT devices

Patch Information

Treck has released patches addressing this vulnerability in version 6.0.1.66 and later of the TCP/IP stack. However, because the Treck stack is embedded within firmware from numerous vendors, organizations must apply updates from each device manufacturer. Consult the following vendor advisories for product-specific patches:

• CERT Vulnerability Advisory VU#257161
• Dell Response to Ripple20
• Cisco Security Advisory
• Intel Security Advisory
• NetApp Security Advisory
• Aruba Networks Security Alert

Workarounds

• Disable IPv6 functionality on vulnerable devices where feasible and operationally acceptable
• Implement strict network segmentation using VLANs or firewalls to isolate vulnerable devices
• Deploy intrusion prevention systems (IPS) with Ripple20-specific rules at network boundaries
• Block or filter IPv6 traffic at network perimeters if IPv6 is not required for operations
• Use network access control (NAC) to restrict which systems can communicate with vulnerable devices

# Example: Disable IPv6 on Linux-based network interfaces (if applicable)
sysctl -w net.ipv6.conf.all.disable_ipv6=1
sysctl -w net.ipv6.conf.default.disable_ipv6=1
# Make persistent across reboots
echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf
echo "net.ipv6.conf.default.disable_ipv6 = 1" >> /etc/sysctl.conf