CVE-2021-20723: Reflected cross-site scripting vulnerability in [MailForm01] free edition (versions which the last updated dat

Routine

MEDIUM 6.1UPGRADE

CVE-2021-20723 is a medium-severity flaw (CVSS 6.1) affecting mailform01. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Reflected cross-site scripting vulnerability in [MailForm01] free edition (versions which the last updated date listed at the top of descriptions in the program file is from 2014 December 12 to 2018 July 27) allows a remote attacker to inject an arbitrary script via unspecified vectors.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-05-24
Last modified	2026-06-17

Publisher (CNA): JPCERT/CC · Vendor: mailform01 project

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

Am I affected?

Timeline

2021-05-24 04:15 UTCPublished CVE record published
2026-06-17 03:34 UTCUpdated Record last modified

mailform01 project mailform01 UPGRADE

Affected: >= 2014-12-12 and <= 2018-07-27

Fixed in: newer than 2018-07-27

Safe to downgrade to: a release before 2014-12-12

1. Check installed version

apt-cache policy mailform01 || rpm -q mailform01 || mailform01 --version

2. UPGRADE to newer than 2018-07-27 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mailform01

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mailform01

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 2014-12-12 (Debian / Ubuntu)

apt-cache madison mailform01 sudo apt install mailform01=<VERSION_BEFORE_2014-12-12> sudo apt-mark hold mailform01

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

dnf --showduplicates list mailform01 sudo dnf downgrade mailform01-<VERSION_BEFORE_2014-12-12> sudo dnf versionlock add mailform01

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-2021-20723?

mailform01: upgrade to newer than 2018-07-27. Exact commands for each OS are on this page.

Is CVE-2021-20723 being exploited?

CVE-2021-20723 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-2021-20723 affect?

CVE-2021-20723 affects mailform01. Severity is medium (CVSS 6.1). Reflected cross-site scripting vulnerability in [MailForm01] free edition (versions which the last updated date listed at the top of descriptions in the program file is from 2014 December 12 to 2018 July 27) allows a remote attacker to inje

How urgent is CVE-2021-20723?

Priority 35/100. No elevated risk signals yet.

References

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