CVE-2021-30175: ZEROF Web Server 1.0 (April 2021) allows SQL Injection via the /HandleEvent endpoint for the login page.

This week

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-30175 is a critical-severity flaw (CVSS 9.8) affecting web server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

ZEROF Web Server 1.0 (April 2021) allows SQL Injection via the /HandleEvent endpoint for the login page.

Why this priority

Critical severity
EPSS top 5%: very likely to be exploited
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	8.5% (top 5%)
CISA exploited list	No
Weakness	CWE-89
Published	2021-04-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: zerof

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-04-13 14:15 UTCPublished CVE record published
2026-06-17 03:49 UTCUpdated Record last modified

zerof web server DOWNGRADE

Affected: 1.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0

1. Check installed version

apt-cache policy web-server || rpm -q web-server || web-server --version

2. No fixed release: DOWNGRADE to a release before 1.0 (Debian / Ubuntu)

apt-cache madison web-server sudo apt install web-server=<VERSION_BEFORE_1.0> sudo apt-mark hold web-server

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list web-server sudo dnf downgrade web-server-<VERSION_BEFORE_1.0> sudo dnf versionlock add web-server

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: ZEROF Web Server 1.0 - SQL Injection

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-30175?

web server: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-30175 being exploited?

CVE-2021-30175 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-30175 affect?

CVE-2021-30175 affects web server. Severity is critical (CVSS 9.8). ZEROF Web Server 1.0 (April 2021) allows SQL Injection via the /HandleEvent endpoint for the login page.

How urgent is CVE-2021-30175?

Priority 63/100. Critical severity; EPSS top 5%: very likely to be exploited; Remotely exploitable, no login, no user action

Related CVEs

CVE-2022-25323 MEDIUM 6.1 DOWNGRADE ZEROF Web Server 2.0 allows /admin.back XSS.
CVE-2022-25322 CRITICAL 9.8 DOWNGRADE ZEROF Web Server 2.0 allows /HandleEvent SQL Injection.
CVE-2018-25235 MEDIUM 6.2 UPGRADE NetworkActiv Web Server 4.0 contains a buffer overflow vulnerability in the username field of the Security opt

References

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