CVE-2021-44273: e2guardian v5.4.x <= v5.4.3r is affected by missing SSL certificate validation in the SSL MITM engine

Q: How urgent is CVE-2021-44273?

Priority 52/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.4REMOTEUPGRADE

CVE-2021-44273 is a high-severity flaw (CVSS 7.4) affecting e2guardian. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

e2guardian v5.4.x <= v5.4.3r is affected by missing SSL certificate validation in the SSL MITM engine. In standalone mode (i.e., acting as a proxy or a transparent proxy), with SSL MITM enabled, e2guardian, if built with OpenSSL v1.1.x, did not validate hostnames in certificates of the web servers that it connected to, and thus was itself vulnerable to MITM attacks.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-295
Published	2021-12-23
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: e2bn

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

Am I affected?

Timeline

2021-12-23 12:15 UTCPublished CVE record published
2026-06-17 04:12 UTCUpdated Record last modified

e2bn e2guardian UPGRADE

Affected: >= 5.4.0 and <= 5.4.3r

Fixed in: newer than 5.4.3r

Safe to downgrade to: a release before 5.4.0

1. Check installed version

apt-cache policy e2guardian || rpm -q e2guardian || e2guardian --version

2. UPGRADE to newer than 5.4.3r (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade e2guardian

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade e2guardian

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.4.0 (Debian / Ubuntu)

apt-cache madison e2guardian sudo apt install e2guardian=<VERSION_BEFORE_5.4.0> sudo apt-mark hold e2guardian

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list e2guardian sudo dnf downgrade e2guardian-<VERSION_BEFORE_5.4.0> sudo dnf versionlock add e2guardian

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.

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-2021-44273?

e2guardian: upgrade to newer than 5.4.3r. Exact commands for each OS are on this page.

Is CVE-2021-44273 being exploited?

CVE-2021-44273 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-2021-44273 affect?

CVE-2021-44273 affects e2guardian. Severity is high (CVSS 7.4). e2guardian v5.4.x <= v5.4.3r is affected by missing SSL certificate validation in the SSL MITM engine. In standalone mode (i.e., acting as a proxy or a transparent proxy), with SSL MITM enabled, e2guardian, if built with OpenSSL v1.1.x, did

How urgent is CVE-2021-44273?

Priority 52/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

OpenSSL vulnerabilities

References

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