What is CVE-2021-4097?

CVE-2021-4097 is a medium-severity vulnerability in Phpservermon Phpservermon/phpservermon, classified under CRLF Injection. CVSS score: 5.4/10. Published 2021-12-12.

How severe is CVE-2021-4097?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Vulnerability in Phpservermon Phpservermon/phpservermon

CVE-2021-4097

phpservermon is vulnerable to Improper Neutralization of CRLF Sequences

Vulnerability class: CRLF Injection

Published 2021-12-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.008 (56.3th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.3% 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

Phpservermon Phpservermon/phpservermon — versions unspecified
Phpservermonitor PHP Server Monitor

Weakness classification (CWE)

CWE-93 — CRLF Injection

References

huntr.dev/bounties/d617ced7-be06-4e34-9db0-63d45c003a43 (Exploit, Patch, Third Party Advisory)
github.com/phpservermon/phpservermon/commit/162bba0046fcda1580f4fbc7b9ababe3c7c… (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-4097?: CVE-2021-4097 is a medium-severity vulnerability in Phpservermon Phpservermon/phpservermon, classified under CRLF Injection. CVSS score: 5.4/10. Published 2021-12-12.
How severe is CVE-2021-4097?: Medium severity. CVSS v3 base score is 5.4 out of 10.