What is CVE-2021-42338?

CVE-2021-42338 is a critical-severity vulnerability in 4mosan Gcb Doctor, classified under Improper Authorization. CVSS score: 9.8/10. Published 2021-11-19.

How severe is CVE-2021-42338?

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

Auth bypass in 4mosan Gcb Doctor

CVE-2021-42338

4MOSAn GCB Doctor’s login page has improper validation of Cookie, which allows an unauthenticated remote attacker to bypass authentication by code injection in cookie, and arbitrarily manipulate the system or interrupt services by upload and execution of arbitrary files.

Published 2021-11-19 · 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: 0.058 (92.9th percentile), scored 2026-10-04.

Low probability of exploitation in the next 30 days, but still tracked. 93rd percentile — 92.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.056 · newest: 0.058 · change: +0.002

Affected products

4mosan Gcb Doctor — versions unspecified
4mosan Gcb Doctor

Weakness classification (CWE)

References

www.twcert.org.tw/tw/cp-132-5313-45bde-1.html (Third Party Advisory)

Frequently asked questions

What is CVE-2021-42338?: CVE-2021-42338 is a critical-severity vulnerability in 4mosan Gcb Doctor, classified under Improper Authorization. CVSS score: 9.8/10. Published 2021-11-19.
How severe is CVE-2021-42338?: Critical severity. CVSS v3 base score is 9.8 out of 10.