Skip to content

CVE-2026-48164 Reflected HTML injection in Collabora Online cool.html

Moderate
caolanm published GHSA-wgmm-q3ch-64jj Jun 24, 2026

Package

coolwsd (collabora online)

Affected versions

< 25.04.11
< 24.04.18

Patched versions

25.04.11
24.04.18

Description

Impact

A reflected XSS vulnerability was found in Collabora Online. The host_session_id query/form parameter was substituted into the editor HTML page without HTML encoding, unlike other parameters which are routed through the existing variable-encoding mechanism. An attacker who could induce a victim to load a crafted URL could inject HTML into the editor page and, in the absence of a Content Security Policy, execute scripts in the context of the Collabora Online iframe. This exposes the session's authentication token and the page contents to the attacker.

Patches

Users should upgrade to Collabora Online 25.04.11 or higher; Collabora Online 24.04.18 or higher.

Workarounds

Ensure that any reverse proxy in front of Collabora Online does not strip the Content Security Policy header sent by coolwsd.

Credits

Thanks to @cristibtz for reporting this flaw.

For more information

If you have any questions or comments about this advisory:

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

CVE ID

CVE-2026-48164

Weaknesses

Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as <, >, and & that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. Learn more on MITRE.

Credits