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CISA KEV · ACTIVELY EXPLOITED
MEDIUM severity

CVE-2025-48700 — zm-build

MEDIUM

CVE-2025-48700 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-04-20) — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.

Published
Updated
Affected
1 product
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-04-20. Federal agencies were required to remediate by 2026-04-23.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2025-48700.

EPSS Exploitation Probability

via FIRST.org ↗
1.7%probability of exploitation in next 30 days
Lower Risk-0.05%
Lower risk than most CVEs77th percentile — riskier than 77% of all scored CVEsHighest risk
0.00%7.71%15.4%23.1%18.2%1.8%1.8%1.7%Jun 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2025-48700 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

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

1 product · 94 configurations
Application
zimbra collaboration suitesynacor
≥ 10.1.0 && < 10.1.4
2 versions
8.8.159.0.0

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Fix

    Upgrade the affected component to the fixed release for CVE-2025-48700, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

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, req
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CVE-2025-48700: zm-build XSS (Medium 6.1, KEV)