CVE-2018-11101

CVE-2018-11101 is a medium-severity vulnerability in Signal Signal-desktop with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

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).

Frequently asked questions

What is CVE-2018-11101?
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).
How severe is CVE-2018-11101?
CVE-2018-11101 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2018-11101 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-11101?
CVE-2018-11101 affects Signal Signal-desktop. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-11101?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2018-11101 published?
CVE-2018-11101 was published on 2018-05-17 and last updated on 2026-06-17.

References

Affected products (1)

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