XSS in HtmlSanitizer

中 6.1CVE-2020-26293 · GHSA-8j9v-h2vp-2hhv · 04/01/2021 公開 · 17/06/2026 更新

要点

CVE-2020-26293 は HtmlSanitizer, htmlsanitizer (htmlsanitizer project) に影響する深刻度「中」 (CVSS 6.1) の脆弱性です。
今後30日間に悪用される確率（EPSS）：1.0%（全脆弱性の 63.3% より高い）。
対処：5.0.372 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
HtmlSanitizer NuGet	`< 5.0.372`	`5.0.372`
htmlsanitizer htmlsanitizer_project	`< 5.0.372`	`5.0.372`

概要

Impact

If you have explicitly allowed the <style> tag, an attacker could craft HTML that includes script after passing through the sanitizer. The default settings disallow the <style> tag so there is no risk if you have not explicitly allowed the <style> tag.

Patches

The problem has been fixed in version 5.0.372.

Workarounds

Remove the <style> tag from the set of allowed tags.

For more information

If you have any questions or comments about this advisory open an issue in https://github.com/mganss/HtmlSanitizer

Credits

This issue was discovered by Michal Bentkowski of Securitum.

NVD の説明

HtmlSanitizer is a .NET library for cleaning HTML fragments and documents from constructs that can lead to XSS attacks. In HtmlSanitizer before version 5.0.372, there is a possible XSS bypass if style tag is allowed. If you have explicitly allowed the `<style>` tag, an attacker could craft HTML that includes script after passing through the sanitizer. The default settings disallow the `<style>` tag so there is no risk if you have not explicitly allowed the `<style>` tag. The problem has been fixed in version 5.0.372.