No exploitation reportedFix available

CVE-2018-20160

Q: Is CVE-2018-20160 actively exploited?

Active exploitation of CVE-2018-20160 has not been confirmed. Its EPSS score was 2.2% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2018-20160?

CVE-2018-20160 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2019-05-29
Fixed in8.8.9 · 8.7.11
WeaknessCWE-611

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

ZxChat (aka ZeXtras Chat), as used for zimbra-chat and zimbra-talk in Synacor Zimbra Collaboration Suite 8.7 and 8.8 and in other products, allows XXE attacks, as demonstrated by a crafted XML request to mailboxd.

Timeline

dates in UTC

2019-05-2922:29CVE publishedNVD

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-2018-20160?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2018-20160?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Synacor zimbra collaboration suite

Branch	Affected	Fixed in	Source
8.8	≥ 8.8.0, < 8.8.9	8.8.9	NVD
8.7	≥ 8.7.0, < 8.7.11	8.7.11	NVD
8.7	= 8.7.11	no fix published	NVD
8.8	= 8.8.9	no fix published	NVD
8.8	= 8.8.10	no fix published	NVD
8.8	= 8.8.11	no fix published	NVD

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

Fix

Update Synacor zimbra collaboration suite to 8.8.9 · 8.7.11

Advisories and patches

wiki.zimbra.comRelease Notes · Vendor Advisory
wiki.zimbra.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.09.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
NVDweakness (CWE)CWE-611read 2026-10-23
FIRST EPSSEPSS score2.2 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2019-05-29
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2018-20160?

Is CVE-2018-20160 actively exploited?

Active exploitation of CVE-2018-20160 has not been confirmed. Its EPSS score was 2.2% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2018-20160?

CVE-2018-20160 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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