Exploited CVEs / Synacor / CVE-2018-6882

CVE-2018-6882

Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2022-05-10 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Zimbra Security Center, linked below.

Risk summary

MediumCISA KEVRansomware

6.1

CVSS base

25%

EPSS exploit probability

Medium

Severity

2022-04-19

Added to KEV

2022-05-10 (past due)

CISA due date

Actively exploited Synacor Zimbra Collaboration Suite (ZCS) vulnerability, Medium severity, CVSS 6.1. Added to the CISA KEV catalog 2022-04-19.

Senserva AI read on CVE-2018-6882 CISA required action Official fix for CVE-2018-6882 Admin questions

Senserva AI Opinion for CVE-2018-6882

Zimbra Collaboration Suite webmail is subject to a cross-site scripting flaw that injects attacker script or HTML into user sessions, and it earned both a KEV listing and a ransomware association, since mail servers are a favorite ransomware entry point. XSS against webmail translates to mailbox access and internal phishing from trusted accounts. Medium Severity at CVSS 6.1, with the risk concentrated in self-hosted Zimbra deployments that lag on patches.

Do this: Bring self-hosted Zimbra servers to a current release and review admin and user session logs for anomalous activity.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2018-6882

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2018-6882, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2018-6882.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2018-6882: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability
- Affected: Synacor Zimbra Collaboration Suite (ZCS)
- Severity: Medium, CVSS 6.1; EPSS 30-day exploitation probability 25%
- Added to CISA KEV: 2022-04-19; federal remediation due 2022-05-10
- Ransomware-linked: YES
- CISA required action: Apply updates per vendor instructions.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch immediately

Exploited in the wild and used in ransomware campaigns.

The fix ships from the vendor: Zimbra Security Center.

Do this now: Move this ahead of everything else in the queue, then verify the fix actually landed on every exposed device.

Updated August 14, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2018-6882

Published: 2022-04-19
Last revised: 2022-04-19
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.

2022-04-19 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 6.1; EPSS first scored at 23.7%
2026-08-03 EPSS 23.7% to 25.2%
2026-08-11 EPSS 25.2% to 25.4%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2022-05-10 (past due).

Apply updates per vendor instructions.

Official fix for CVE-2018-6882

The authoritative fix and affected-version list are published by the vendor. Find the Zimbra Collaboration Suite (ZCS) advisory on Zimbra Security Center.

Zimbra Security Center CISA KEV entry

Common questions about CVE-2018-6882

Is CVE-2018-6882 actively exploited?

Yes. CVE-2018-6882 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2022-04-19, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 25%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2018-6882?

CISA set the federal (BOD 22-01) remediation due date at 2022-05-10, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.

What fixes CVE-2018-6882?

The authoritative fix is in the vendor advisory: see Zimbra Security Center for the patched Zimbra Collaboration Suite (ZCS) versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2018-6882?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2018-6882's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited Synacor CVEs: CVE-2025-48700 CVE-2025-66376 CVE-2020-7796 CVE-2025-68645 CVE-2025-27915 CVE-2019-9621 CVE-2024-27443 CVE-2023-34192
All Synacor exploited CVEs on one page: Synacor vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.