What is CVE-2021-21727?

CVE-2021-21727 is a high-severity vulnerability in ZTE Zxhn F623. CVSS score: 7.5/10. Published 2021-03-29.

How severe is CVE-2021-21727?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in ZTE Zxhn F623

CVE-2021-21727

A ZTE product has a DoS vulnerability. A remote attacker can amplify traffic by sending carefully constructed IPv6 packets to the affected devices, which eventually leads to device denial of service. This affects:<ZXHN F623><All versions up to V6.0.0P3T33>

Published 2021-03-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.014 (71.2th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 71st percentile — 71.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.014 · change: 0.000

Affected products

ZTE Zxhn F623
ZTE Zxhn F623 Firmware
<zxhn F623> — versions <ZXHN Z500 V1.0.0.2B1.1000 & ZXHN F670L V1.1.10P1N2E>

References

support.zte.com.cn/support/news/LoopholeInfoDetail.aspx (Vendor Advisory)

Frequently asked questions

What is CVE-2021-21727?: CVE-2021-21727 is a high-severity vulnerability in ZTE Zxhn F623. CVSS score: 7.5/10. Published 2021-03-29.
How severe is CVE-2021-21727?: High severity. CVSS v3 base score is 7.5 out of 10.