Public proof of concept

CVE-2016-9920

A public proof of concept exists; no exploitation attested.

Published2016-12-08
WeaknessCWE-284

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

steps/mail/sendmail.inc in Roundcube before 1.1.7 and 1.2.x before 1.2.3, when no SMTP server is configured and the sendmail program is enabled, does not properly restrict the use of custom envelope-from addresses on the sendmail command line, which allows remote authenticated users to execute arbitrary code via a modified HTTP request that sends a crafted e-mail message.

Timeline

dates in UTC

2016-12-0818:59CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2016-9920?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2016-9920?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Roundcube webmail

Branch	Affected	Fixed in	Source
1.1	≤ 1.1.6	no fix published	NVD
1.2	= 1.2.0	no fix published	NVD
1.2	= 1.2.1	no fix published	NVD
1.2	= 1.2.2	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

roundcube.netRelease Notes · Vendor Advisory

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedt0kx/exploit-CVE-2016-9920

Sources

NVDCVSS 3.07.5read 2026-10-23
NVDCVSS 2.06read 2026-10-23
NVDweakness (CWE)CWE-284read 2026-10-23
FIRST EPSSEPSS score5.6 %2026-10-22
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Published: 2016-12-08
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2016-9920?

Is CVE-2016-9920 actively exploited?

Active exploitation of CVE-2016-9920 has not been confirmed. Its EPSS score was 5.6% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2016-9920?

CVE-2016-9920 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.

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