CVE-2018-19991: VeryNginx 0.3.3 allows remote attackers to bypass the Web Application Firewall feature because there is no err

This week

CRITICAL 9.8REMOTEWATCHLISTDOWNGRADE

CVE-2018-19991 is a critical-severity flaw (CVSS 9.8) affecting verynginx. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

VeryNginx 0.3.3 allows remote attackers to bypass the Web Application Firewall feature because there is no error handler (for get_uri_args or get_post_args) to block the API misuse described in CVE-2018-9230.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.3% (top 17%)
CISA exploited list	No
Weakness	CWE-755
Published	2018-12-10
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: verynginx project

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

Am I affected?

Timeline

2018-12-10 00:29 UTCPublished CVE record published
2026-06-17 01:50 UTCUpdated Record last modified

verynginx project verynginx DOWNGRADE

Affected: 0.3.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.3.3

1. Check installed version

apt-cache policy verynginx || rpm -q verynginx || verynginx --version

2. No fixed release: DOWNGRADE to a release before 0.3.3 (Debian / Ubuntu)

apt-cache madison verynginx sudo apt install verynginx=<VERSION_BEFORE_0.3.3> sudo apt-mark hold verynginx

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

dnf --showduplicates list verynginx sudo dnf downgrade verynginx-<VERSION_BEFORE_0.3.3> sudo dnf versionlock add verynginx

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · copyparty · FIXED · 1.20.26-1.fc46 · FEDORA-2026-8fbe18458e · source

sudo dnf upgrade --advisory=FEDORA-2026-8fbe18458e

Fedora ELN · man-pages · FIXED · 6.20-1.eln159 · FEDORA-2026-f1f5fb11b4 · source

sudo dnf upgrade --advisory=FEDORA-2026-f1f5fb11b4

Public exploits and detection

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

Write-up: github.com/alexazhou/VeryNginx/issues/218

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-2018-19991?

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

Is CVE-2018-19991 being exploited?

CVE-2018-19991 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-2018-19991 affect?

CVE-2018-19991 affects verynginx. Severity is critical (CVSS 9.8). VeryNginx 0.3.3 allows remote attackers to bypass the Web Application Firewall feature because there is no error handler (for get_uri_args or get_post_args) to block the API misuse described in CVE-2018-9230.

How urgent is CVE-2018-19991?

Priority 70/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

References

← Back to latest CVEs