How severe is CVE-2018-20160?

CVE-2018-20160 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2018-20160 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-20160?

CVE-2018-20160 primarily affects Synacor Zimbra Collaboration Suite. In total, 24 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-20160?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2018-20160 published?

CVE-2018-20160 was published on 2019-05-29 and last updated on 2026-06-17.

CVE-2018-20160

CVE-2018-20160 is a critical-severity vulnerability in Synacor Zimbra Collaboration Suite with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-611.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-611
Affected product: Synacor Zimbra Collaboration Suite
Published: 2019-05-29
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2018-20160?: 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.
How severe is CVE-2018-20160?: CVE-2018-20160 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2018-20160 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-20160?: CVE-2018-20160 primarily affects Synacor Zimbra Collaboration Suite. In total, 24 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-20160?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2018-20160 published?: CVE-2018-20160 was published on 2019-05-29 and last updated on 2026-06-17.

References

Affected products (24)

cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:-:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p1:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p2:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p3:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p4:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p5:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p6:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p7:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p8:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.7.11:p9:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:-:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:p1:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:p2:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:p3:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:p4:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:p6:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:p7:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.9:p8:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.10:-:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.10:p2:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.10:p3:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.10:p4:*:*:*:*:*:*
cpe:2.3:a:synacor:zimbra_collaboration_suite:8.8.11:-:*:*:*:*:*:*

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