CVE-2018-18621: CommuniGate Pro 6.2 allows stored XSS via a message body in Pronto! Mail Composer, which is mishandled in /MIM

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MEDIUM 6.1DOWNGRADE

CVE-2018-18621 is a medium-severity flaw (CVSS 6.1) affecting communigate pro. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

CommuniGate Pro 6.2 allows stored XSS via a message body in Pronto! Mail Composer, which is mishandled in /MIME/INBOX-MM-1/ if the raw email link (in .txt format) is modified and then renamed with a .html or .wssp extension.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.1% (top 36%)
CISA exploited list	No
Weakness	CWE-79
Published	2018-10-24
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: communigate

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

Am I affected?

Timeline

2018-10-24 22:29 UTCPublished CVE record published
2026-06-17 01:47 UTCUpdated Record last modified

communigate communigate pro DOWNGRADE

Affected: 6.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.2

1. Check installed version

apt-cache policy communigate-pro || rpm -q communigate-pro || communigate-pro --version

2. No fixed release: DOWNGRADE to a release before 6.2 (Debian / Ubuntu)

apt-cache madison communigate-pro sudo apt install communigate-pro=<VERSION_BEFORE_6.2> sudo apt-mark hold communigate-pro

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

dnf --showduplicates list communigate-pro sudo dnf downgrade communigate-pro-<VERSION_BEFORE_6.2> sudo dnf versionlock add communigate-pro

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-2018-18621?

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

Is CVE-2018-18621 being exploited?

CVE-2018-18621 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-2018-18621 affect?

CVE-2018-18621 affects communigate pro. Severity is medium (CVSS 6.1). CommuniGate Pro 6.2 allows stored XSS via a message body in Pronto! Mail Composer, which is mishandled in /MIME/INBOX-MM-1/ if the raw email link (in .txt format) is modified and then renamed with a .html or .wssp extension.

How urgent is CVE-2018-18621?

Priority 42/100. Public exploit reference

Related CVEs

CVE-2018-3815 MEDIUM 5.7 DOWNGRADE The "XML Interface to Messaging, Scheduling, and Signaling" (XIMSS) protocol implementation in CommuniGate Pro
CVE-2017-16962 MEDIUM 6.1 UPGRADE The WebMail components (Crystal, pronto, and pronto4) in CommuniGate Pro before 6.2.1 have stored XSS vulnerab

References

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