CVE-2018-16736: In the rcfilters plugin 2.1.6 for Roundcube, XSS exists via the _whatfilter and _messages parameters (in the F

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MEDIUM 5.4DOWNGRADE

CVE-2018-16736 is a medium-severity flaw (CVSS 5.4) affecting rcfilters. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In the rcfilters plugin 2.1.6 for Roundcube, XSS exists via the _whatfilter and _messages parameters (in the Filters section of the settings).

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	2.6% (top 15%)
CISA exploited list	No
Weakness	CWE-79
Published	2018-09-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: rcfilters project

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

Am I affected?

Timeline

2018-09-09 12:29 UTCPublished CVE record published
2026-06-17 01:44 UTCUpdated Record last modified

rcfilters project rcfilters DOWNGRADE

Affected: 2.1.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.1.6

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.1.6 (Debian / Ubuntu)

apt-cache madison rcfilters sudo apt install rcfilters=<VERSION_BEFORE_2.1.6> sudo apt-mark hold rcfilters

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

dnf --showduplicates list rcfilters sudo dnf downgrade rcfilters-<VERSION_BEFORE_2.1.6> sudo dnf versionlock add rcfilters

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.

Exploit-DB: Roundcube rcfilters plugin 2.1.6 - Cross-Site Scripting

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-2018-16736?

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

Is CVE-2018-16736 being exploited?

CVE-2018-16736 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-2018-16736 affect?

CVE-2018-16736 affects rcfilters. Severity is medium (CVSS 5.4). In the rcfilters plugin 2.1.6 for Roundcube, XSS exists via the _whatfilter and _messages parameters (in the Filters section of the settings).

How urgent is CVE-2018-16736?

Priority 45/100. Public exploit reference

Software pages

Roundcube vulnerabilities

References

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