CVE-2023-40891Network attack vector

Unauthenticated router crash via firewallEn stack overflow

Published Aug 24, 2023 · Updated Oct 3, 2024

Stack overflow in Tenda AC8 v4.0 firmware US_AC8V4.0si_V16.03.34.06_cn allows remote attackers to crash the router. The /goform/SetFirewallCfg handler writes an oversized firewallEn request parameter beyond a stack buffer without enforcing its destination size. The endpoint is network-reachable without authentication; crafted input corrupts process memory, while public evidence demonstrates a device crash but not code execution.

CVSS severity9.8
Critical
EPSS probability0.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Stack overflow in Tenda AC8 v4.0 firmware US_AC8V4.0si_V16.03.34.06_cn allows remote attackers to crash the router. The /goform/SetFirewallCfg handler writes an oversized firewallEn request parameter beyond a stack buffer without enforcing its destination size. The endpoint is network-reachable without authentication; crafted input corrupts process memory, while public evidence demonstrates a device crash but not code execution.

The record

CVE
CVE-2023-40891
Published
Aug 24, 2023
Updated
Oct 3, 2024
Vendor
Shenzhen Tenda Technology Co., Ltd.
Product
AC8 v4.0
Classifications
CWE-787, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 24, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=US_AC8V4.0si_V16.03.34.06_cn

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Shenzhen Tenda Technology Co., Ltd. · AC8 v4.0version=US_AC8V4.0si_V16.03.34.06_cn

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo