Open Whisper Signal up to 1.10.1 script/iframe/img cross site scripting

Summaryinfo

A vulnerability, which was classified as critical, has been found in Open Whisper Signal up to 1.10.1. This impacts an unknown function. Performing a manipulation of the argument script/iframe/img results in cross site scripting. This vulnerability is identified as CVE-2018-11101. The attack can be initiated remotely. Additionally, an exploit exists.

Detailsinfo

A vulnerability was found in Open Whisper Signal up to 1.10.1. It has been classified as critical. This affects an unknown functionality. The manipulation of the argument script/iframe/img with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as 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. This is going to have an impact on integrity. The summary by CVE is:

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 operative 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).

The bug was discovered 05/14/2018. The weakness was released 05/17/2018 as not defined mailinglist post (Full-Disclosure). It is possible to read the advisory at seclists.org. This vulnerability is uniquely identified as CVE-2018-11101 since 05/14/2018. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details and a public exploit are known. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

The exploit is shared for download at packetstormsecurity.com. It is declared as proof-of-concept. The vulnerability was handled as a non-public zero-day exploit for at least 3 days. During that time the estimated underground price was around $5k-$25k.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• Open Whisper Signal

Version

• 1.10.0
• 1.10.1

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