How severe is CVE-2023-44390?

CVE-2023-44390 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-44390?

CVE-2023-44390 affects the following packages: HtmlSanitizer (NuGet), HtmlSanitizer (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2023-44390?

Update HtmlSanitizer to 8.0.723 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-44390 is resolved across your whole dependency graph.

How do I detect CVE-2023-44390 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for HtmlSanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2023-44390 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2023-44390 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-44390 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-44390?

CVE-2023-44390 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 36th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-44390?

CVE-2023-44390 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2023-44390 published, and has it been updated?

CVE-2023-44390 was published on October 5, 2023 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET

.NET NuGet

Not in CISA KEV

MEDIUM severity

CVE-2023-44390 — HtmlSanitizer

MEDIUMFix: mganss/HtmlSanitizer@ab29319

CVE-2023-44390 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in HtmlSanitizer. A fix is available for HtmlSanitizer — see the affected versions and patch details below.

HtmlSanitizer vulnerable to Cross-site Scripting in Foreign Content

Also known asGHSA-43cp-6p3q-2pc4

Published

Oct 5, 2023

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-44390.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs36th percentile — riskier than 36% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

.NETHtmlSanitizer.NETHtmlSanitizer

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

Impact

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:

Allowing one foreign element: svg, or math
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.

Patches

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

Workarounds

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

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`HtmlSanitizer`	all versions	8.0.723`dotnet add package HtmlSanitizer --version 8.0.723`
.NETNuGet	`HtmlSanitizer`	≥ 8.1.0-beta&&< 8.1.722-beta	8.1.722-beta`dotnet add package HtmlSanitizer --version 8.1.722-beta`

Affected Products

1 product · 2 configurations

Application

htmlsanitizerhtmlsanitizer_project

< 8.0.723

1 version

8.1.719

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for HtmlSanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update HtmlSanitizer to 8.0.723 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-44390 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact 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 a