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Known Exploited Vulnerability
5.4
MEDIUM CVSS 3.1
CVE-2025-27915
Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability - [Actively Exploited]
Description

An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a <details> tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.

INFO

Published Date :

March 12, 2025, 3:15 p.m.

Last Modified :

Oct. 8, 2025, 12:48 p.m.

Remotely Exploit :

Yes !

Source :

[email protected]
CISA Notification
CISA KEV (Known Exploited Vulnerabilities)

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.

Description :

Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.

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.

Notes :

https://wiki.zimbra.com/wiki/Security_Center ; https://nvd.nist.gov/vuln/detail/CVE-2025-27915

Affected Products

The following products are affected by CVE-2025-27915 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Zimbra collaboration
: Total Affected Vendor : 1 | Products : 1
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 3.1 MEDIUM 134c704f-9b21-4f2e-91b3-4a467353bcc0
Solution
Sanitize HTML content in ICS files to prevent stored XSS attacks.
  • Sanitize HTML content in ICS files.
  • Update affected Zimbra Collaboration versions.
  • Validate user input for ICS processing.
  • Avoid rendering untrusted HTML directly.
Public PoC/Exploit Available at Github

CVE-2025-27915 has a 1 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2025-27915.

URL Resource
https://wiki.zimbra.com/wiki/Security_Center Release Notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes Release Notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes Release Notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes Release Notes
https://strikeready.com/blog/0day-ics-attack-in-the-wild/ Exploit Third Party Advisory
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2025-27915 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2025-27915 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Profile Photo
maldua-pimbra/maldua-pimbra

Main repo about patched Zimbra repos

Updated: 3 months ago
3 stars 0 fork 0 watcher
Born at : March 20, 2025, 1 p.m. This repo has been linked 1 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2025-27915 vulnerability anywhere in the article.

  • Daily CyberSecurity
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  • The Hacker News
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  • The Cyber Express
CISA Warns of Actively Exploited Zero-Day XSS Flaw in Zimbra Collaboration Suite

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) have issued an urgent alert concerning an actively exploited zero-day vulnerability in the Zimbra Collaboration Suite (ZCS). The flaw, ... Read more

Published Date: Oct 09, 2025 (19 hours, 26 minutes ago)
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Published Date: Oct 09, 2025 (1 day ago)
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Published Date: Oct 09, 2025 (1 day, 2 hours ago)
  • Daily CyberSecurity
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Published Date: Oct 09, 2025 (1 day, 2 hours ago)
  • CybersecurityNews
CISA Warns of Zimbra Collaboration Suite (ZCS) XSS Zero-Day Vulnerability Actively Exploited in Attacks

CISA has issued a critical warning regarding a zero-day cross-site scripting (XSS) vulnerability in Synacor’s Zimbra Collaboration Suite (ZCS), designated as CVE-2025-27915. This vulnerability has bee ... Read more

Published Date: Oct 08, 2025 (1 day, 18 hours ago)
  • Daily CyberSecurity
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Published Date: Oct 08, 2025 (1 day, 22 hours ago)
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Published Date: Oct 08, 2025 (1 day, 22 hours ago)
  • Daily CyberSecurity
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Published Date: Oct 08, 2025 (1 day, 22 hours ago)
  • Daily CyberSecurity
Zimbra XSS Zero-Day (CVE-2025-27915) Actively Exploited; CISA Adds to KEV Catalog

A cross-site scripting (XSS) vulnerability in Synacor Zimbra Collaboration Suite (ZCS) — tracked as CVE-2025-27915 — has been confirmed to be actively exploited in the wild, prompting CISA to add the ... Read more

Published Date: Oct 08, 2025 (1 day, 23 hours ago)

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2025-27915 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • Modified Analysis by [email protected]

    Oct. 08, 2025

    Action Type Old Value New Value
    Added Reference Type CISA-ADP: https://strikeready.com/blog/0day-ics-attack-in-the-wild/ Types: Exploit, Third Party Advisory
  • CVE CISA KEV Update by 9119a7d8-5eab-497f-8521-727c672e3725

    Oct. 08, 2025

    Action Type Old Value New Value
    Added Date Added 2025-10-07
    Added Due Date 2025-10-28
    Added 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.
    Added Vulnerability Name Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Oct. 07, 2025

    Action Type Old Value New Value
    Added Reference https://strikeready.com/blog/0day-ics-attack-in-the-wild/
  • Initial Analysis by [email protected]

    Apr. 02, 2025

    Action Type Old Value New Value
    Added CPE Configuration OR *cpe:2.3:a:zimbra:collaboration:9.0.0:-:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p2:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p3:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p4:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p5:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p6:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p9:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p0:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p1:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p10:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p11:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p12:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p13:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p14:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p15:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p19:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p7:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p8:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p16:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p20:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p21:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p23:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p24:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p24.1:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p25:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p26:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p27:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p28:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p29:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p30:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p31:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p32:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p33:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p34:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p35:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p36:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p37:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p38:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p39:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p40:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p7.1:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:* versions from (including) 10.0.0 up to (excluding) 10.0.13 *cpe:2.3:a:zimbra:collaboration:9.0.0:p41:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p42:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:9.0.0:p43:*:*:*:*:*:* *cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:* versions from (including) 10.1.0 up to (excluding) 10.1.5
    Added Reference Type MITRE: https://wiki.zimbra.com/wiki/Security_Center Types: Release Notes
    Added Reference Type MITRE: https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes Types: Release Notes
    Added Reference Type MITRE: https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes Types: Release Notes
    Added Reference Type MITRE: https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes Types: Release Notes
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Mar. 12, 2025

    Action Type Old Value New Value
    Added CVSS V3.1 AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
    Added CWE CWE-79
  • New CVE Received by [email protected]

    Mar. 12, 2025

    Action Type Old Value New Value
    Added Description An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a <details> tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.
    Added Reference https://wiki.zimbra.com/wiki/Security_Center
    Added Reference https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes
    Added Reference https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes
    Added Reference https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
Vulnerability Scoring Details
Base CVSS Score: 5.4
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact