CVE-2018-11101 Cross-site scripting in n/a

Medium 6.1 Published 17 May 2018 Updated 5 Aug 2024

Attackers can execute arbitrary JavaScript in Signal Desktop by sending crafted HTML messages and replying to them, potentially leading to full system compromise.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2018-11101?

CVE-2018-11101 is a medium-severity cross-site scripting vulnerability in n/a, published on 17 May 2018. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Open Whisper Signal (aka Signal-Desktop) through 1.10.1 allows XSS via a resource location specified in an attribute of a SCRIPT, IFRAME, or IMG element, leading to JavaScript execution after a reply, a different vulnerability than CVE-2018-10994. The attacker needs to send HTML code directly as a message, and then reply to that message to trigger this vulnerability. The Signal-Desktop software fails to sanitize specific HTML elements that can be used to inject HTML code into remote chat windows when replying to an HTML message. Specifically the IMG and IFRAME elements can be used to include remote or local resources. For example, the use of an IFRAME element enables full code execution, allowing an attacker to download/upload files, information, etc. The SCRIPT element was also found to be injectable. On the Windows operating system, the CSP fails to prevent remote inclusion of resources via the SMB protocol. In this case, remote execution of JavaScript can be achieved by referencing the script on an SMB share within an IFRAME element, for example: <IFRAME src=\\DESKTOP-XXXXX\Temp\test.html> and then replying to it. The included JavaScript code is then executed automatically, without any interaction needed from the user. The vulnerability can be triggered in the Signal-Desktop client by sending a specially crafted message and then replying to it with any text or content in the reply (it doesn't matter).

Weakness: CWE-79

Which versions are affected by CVE-2018-11101?

It affects 1 product.

Products include Signal Signal-Desktop.

How do I fix CVE-2018-11101?

No fix has been published for CVE-2018-11101 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2018-11101 being exploited?

There is no known exploitation of CVE-2018-11101 in the wild and no public exploit code.

Sources

Also known as GHSA-hf9p-487c-2v2r.