CVE-2026-67967 Overview
CVE-2026-67967 is a stack-based buffer overflow [CWE-121] affecting the Tenda W20E router, firmware version V16.01.0.6(2782). Remote attackers can exploit the flaw over the network without authentication or user interaction to execute arbitrary code on the device. The advisory notes this issue represents an incomplete fix for two prior vulnerabilities, CVE-2025-44867 and CVE-2026-36819, indicating the vendor patches did not fully close the affected code path. Successful exploitation grants attacker-controlled code execution on the router, which sits at the network perimeter.
Critical Impact
Unauthenticated network attackers can achieve arbitrary code execution on affected Tenda W20E devices, compromising confidentiality, integrity, and availability of the router and downstream network traffic.
Affected Products
- Tenda W20E router
- Firmware version V16.01.0.6(2782)
- Devices previously patched only against CVE-2025-44867 and CVE-2026-36819
Discovery Timeline
- 2026-08-17 - CVE-2026-67967 published to NVD
- 2026-08-18 - Last updated in NVD database
Technical Details for CVE-2026-67967
Vulnerability Analysis
The vulnerability is a stack-based buffer overflow [CWE-121] in the Tenda W20E firmware. Attacker-supplied input exceeds the bounds of a fixed-size stack buffer, corrupting adjacent stack memory, including saved return addresses and control-flow metadata. On embedded MIPS or ARM router firmware without modern exploit mitigations, this class of flaw commonly enables reliable arbitrary code execution.
The advisory explicitly states that CVE-2026-67967 is an incomplete fix for CVE-2025-44867 and CVE-2026-36819. The vendor patch narrowed but did not eliminate the vulnerable code path, leaving a variant reachable by attackers who adjust their payload structure.
Root Cause
The root cause is missing or insufficient bounds checking on attacker-controlled input before it is copied into a stack buffer. Prior fixes addressed specific input vectors but left related paths unprotected, allowing the same primitive to be reached through modified requests.
Attack Vector
Exploitation occurs over the network against the router management interface. The attacker sends a crafted request containing an oversized field. No credentials and no user interaction are required. Refer to the GitHub Vulnerability Disclosure for the technical write-up and reproduction details.
// No verified exploit code is published in the enriched data.
// See the linked disclosure for parameter-level details on the
// vulnerable request and the incomplete patch context.
Detection Methods for CVE-2026-67967
Indicators of Compromise
- Unexpected reboots or crash loops on the Tenda W20E router consistent with stack corruption during request processing.
- Outbound connections from the router to unfamiliar hosts, indicative of implanted code or reverse shells.
- HTTP requests to the router management interface containing unusually long parameter values or non-printable byte sequences.
Detection Strategies
- Inspect network traffic destined for the router administrative interface for oversized parameters targeting endpoints referenced in the linked disclosure.
- Correlate router log anomalies with perimeter firewall telemetry to identify pre-exploit reconnaissance and post-exploit callbacks.
- Baseline expected management-plane traffic and alert on deviations, particularly requests originating from the WAN interface.
Monitoring Recommendations
- Forward router syslog and NetFlow data to a centralized analytics platform for longitudinal review.
- Monitor DNS queries and egress traffic from the router itself, which should be minimal under normal operation.
- Track firmware version and configuration drift on all Tenda W20E devices in inventory.
How to Mitigate CVE-2026-67967
Immediate Actions Required
- Restrict access to the router management interface to trusted management networks only, and disable WAN-side administration.
- Segment the affected devices from sensitive internal assets until a complete fix is available.
- Audit accounts, configuration, and firmware integrity on any device suspected of exposure.
Patch Information
The advisory identifies CVE-2026-67967 as an incomplete fix for CVE-2025-44867 and CVE-2026-36819. No complete vendor patch is referenced in the enriched data. Monitor the GitHub Vulnerability Disclosure and Tenda's official channels for a corrected firmware release, and apply it as soon as it becomes available.
Workarounds
- Place the router behind an upstream firewall that blocks unsolicited inbound traffic to management ports.
- Enforce strong administrative credentials and disable remote management features that expose the vulnerable interface.
- Consider replacing the device with a supported model if a corrected firmware release is not made available in a reasonable timeframe.
# Example: block external access to the router admin interface at an upstream firewall
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -i <wan_iface> -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 443 -i <wan_iface> -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
