Synacor Zimbra Collaborate Suite (ZCS) Cross-Site Scripting Vulnerability

CheckOps priority index

6.4/10 Patch within 7 days

Severity6.1

Probability3.1

Exploitation5/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 30.9% higher than 98.3% of CVEs

CVSS 3.1 6.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:

Exploited for 1,712 days 25 Feb 2022

CISA due date 11 Mar 2022 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 5 / 5

KEV catalog (CISA)25 Feb 2022
Exploited in EUVD (ENISA)25 Feb 2022
Used by ransomwareyes
EPSS above 10 %30.9%
No account, over the networkyes

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply updates per vendor instructions.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Description ENISA EUVD

An issue was discovered in the Calendar feature in Zimbra Collaboration Suite 8.8.x before 8.8.15 patch 30 (update 1), as exploited in the wild starting in December 2021. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document.

Affected products

Zimbra Collaborate Suite (ZCS)

Weaknesses (CWE)

CWE-79 CWE-116

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

09 Feb 2022
Published
25 Feb 2022
Exploitation reported (ENISA)
25 Feb 2022
Added to the KEV catalog
11 Mar 2022
CISA remediation due date
26 Sept 2026
EPSS peak: 30.9%

References

Other exploited vulnerabilities from the same vendor

CVE-2026-73570Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability
8.1 · Actively exploited
CVE-2025-48700Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
4.3 · Background exploitation
CVE-2025-66376Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
5.9 · Background exploitation
CVE-2020-7796Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery Vulnerability
9.1 · Background exploitation
CVE-2025-68645Synacor Zimbra Collaboration Suite (ZCS) PHP Remote File Inclusion Vulnerability
7.4 · Background exploitation
CVE-2025-27915Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
3.5 · Background exploitation