What is CVE-2023-40891?

CVE-2023-40891 is a critical-severity vulnerability in Tenda Ac8 Firmware, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2023-08-24.

How severe is CVE-2023-40891?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2023-40891 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Buffer overflow in Tenda Ac8 Firmware

CVE-2023-40891

Tenda AC8 v4 US_AC8V4.0si_V16.03.34.06_cn was discovered to contain a stack overflow via parameter firewallEn at /goform/SetFirewallCfg.

Vulnerability class: Buffer Overflow

Published 2023-08-24 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.008 (56.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Tenda Ac8 Firmware — versions 16.03.34.06
Tenda Ac8v4

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

Public proof-of-concept exploits

IoTBec/Reports

References

github.com/peris-navince/founded-0-days/blob/main/ac8/formSetFirewallCfg/1.md (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2023-40891?: CVE-2023-40891 is a critical-severity vulnerability in Tenda Ac8 Firmware, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2023-08-24.
How severe is CVE-2023-40891?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2023-40891 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.