Zero-day vulnerability in Zimbra Collaboration

Stored cross-site scripting
CVE-2025-27915

Vulnerability details

Advisory: SB2025100641 - Multiple vulnerabilities in Zimbra Collaboration

Vulnerable component: Zimbra Collaboration

CVE-ID: CVE-2025-27915

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N/E:H/RL:O/RC:C

CWE-ID: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Description:

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data when handling ICS files. A remote attacker can send an email message with a specially crafted calendar attachment and execute arbitrary JavaScript code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

Note, the vulnerability is being actively exploited in the wild.

External links:

https://strikeready.com/blog/0day-ics-attack-in-the-wild/

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.