---
title: "CVE-2025-48700: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability"
url: https://erroneo.us/security/cve/CVE-2025-48700/
description: "CVE-2025-48700 (Synacor Zimbra Collaboration Suite (ZCS)): Exploited in the wild (CISA KEV). An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15…"
type: vulnerability-record
section: "Security Digest"
date_published: 2025-06-23
date_modified: 2026-04-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-48700"
kev: true
cvss: 6.1
epss: 0.01713
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-48700: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Synacor Zimbra Collaboration Suite (ZCS). CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-04-20, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-04-23 ; treat that as the outer limit, not the target.
- EPSS 1.7% , percentile 77: FIRST’s model estimates a 1.7% chance of exploitation activity in the next 30 days, higher than 77% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.

## What it is

An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15 and 9.0 and 10.0 and 10.1. A Cross-Site Scripting (XSS) vulnerability in the Zimbra Classic UI allows attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information. This issue arises from insufficient sanitization of HTML content, specifically involving crafted tag structures and attribute values that include an @import directive and other script injection vectors. The vulnerability is triggered when a user views a crafted e-mail message in the Classic UI, requiring no additional user interaction.

## Affected products (CVE record)

- n/a n/a: see advisory

## Severity

- CISA-ADP CVSS 3.1: 6.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`

## Exploitation

- CISA KEV: added 2026-04-20; federal due date 2026-04-23. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active , automatable no , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 1.71% probability of exploitation activity in the next 30 days; percentile 77.

## Sources

- [Listed in CISA KEV notes (wiki.zimbra.com)](https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories)
- [CVE.org record CVE-2025-48700](https://www.cve.org/CVERecord?id=CVE-2025-48700)
- [NVD entry CVE-2025-48700](https://nvd.nist.gov/vuln/detail/CVE-2025-48700)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-48700)
- [wiki.zimbra.com](https://wiki.zimbra.com/wiki/Security_Center)
- [wiki.zimbra.com](https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy)

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Source page: https://erroneo.us/security/cve/CVE-2025-48700/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt