Collabora Online up to 24.04.17/25.04.10 HTML Encoding cool.html host_session_id HTML injection

Summaryinfo

A vulnerability classified as problematic has been found in Collabora Online up to 24.04.17/25.04.10. This issue affects some unknown processing of the file cool.html of the component HTML Encoding. This manipulation of the argument host_session_id causes HTML injection. The identification of this vulnerability is CVE-2026-48164. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Collabora Online up to 24.04.17/25.04.10 and classified as problematic. Affected by this vulnerability is some unknown processing of the file cool.html of the component HTML Encoding. The manipulation of the argument host_session_id with an unknown input leads to a html injection vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

Collabora Online is a collaborative online office suite based on LibreOffice technology. Prior to 24.04.18 and 25.04.11, the `host_session_id` query/form parameter is substituted into the `cool.html` editor page without HTML encoding, unlike parameters passed through the existing variable-encoding mechanism. An attacker who induces a victim to load a crafted URL can inject HTML and, in the absence of an effective `Content Security Policy`, execute scripts in the Collabora Online iframe's origin, exposing the session authentication token and page contents. A reverse proxy that preserves the `Content Security Policy` header sent by `coolwsd` mitigates the script-execution scenario. This issue is fixed in versions 24.04.18 and 25.04.11.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-48164 since 05/21/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

By approaching the search of inurl:cool.html it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 24.04.18 or 25.04.11 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• Collabora

Name

• Online

Version

• 24.04.0
• 24.04.1
• 24.04.2
• 24.04.3
• 24.04.4
• 24.04.5
• 24.04.6
• 24.04.7
• 24.04.8
• 24.04.9
• 24.04.10
• 24.04.11
• 24.04.12
• 24.04.13
• 24.04.14
• 24.04.15
• 24.04.16
• 24.04.17
• 25.04.0
• 25.04.1
• 25.04.2
• 25.04.3
• 25.04.4
• 25.04.5
• 25.04.6
• 25.04.7
• 25.04.8
• 25.04.9
• 25.04.10

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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