CVE-2023-44390

HtmlSanitizer vulnerable to Cross-site Scripting in Foreign Content

Workarounds

Disallow foreign elements svg and math. This is the case in the default configuration, which is therefore not affected by the vulnerability.

The vulnerability occurs in configurations where foreign content is allowed, i.e. either svg or math are in the list of allowed elements.
Specifically, the requirements for the vulnerability are:

1. Allowing one foreign element: svg, or math
2. Comments or one raw text element: iframe, noembed, xmp, title, noframes, style or noscript

Configurations that meet the above requirements plus the following are vulnerable to an additional vulnerability:

• Any HTML integration element: title, desc, mi, mo, mn, ms, mtext, annotation-xml.

In case an application sanitizes user input with a vulnerable configuration, an attacker could
bypass the sanitization and inject arbitrary HTML, including JavaScript code.

Note that in the default configuration the vulnerability is not present.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2023-44390 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (8.0.723, 8.1.722-beta); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

The vulnerability has been fixed in versions 8.0.723 and 8.1.722-beta (preview version).

1. What is CVE-2023-44390? CVE-2023-44390 is a medium-severity cross-site scripting (XSS) vulnerability in HtmlSanitizer (nuget), affecting versions < 8.0.723. It is fixed in 8.0.723, 8.1.722-beta. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2023-44390? CVE-2023-44390 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of HtmlSanitizer are affected by CVE-2023-44390? HtmlSanitizer (nuget) versions < 8.0.723 is affected.
4. Is there a fix for CVE-2023-44390? Yes. CVE-2023-44390 is fixed in 8.0.723, 8.1.722-beta. Upgrade to this version or later.
5. Is CVE-2023-44390 exploitable, and should I be worried? Whether CVE-2023-44390 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-44390 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-44390?
   • Upgrade HtmlSanitizer to 8.0.723 or later
   • Upgrade HtmlSanitizer to 8.1.722-beta or later

Other vulnerabilities in HtmlSanitizer