What’s Vulnerable › Vulnerabilities
CVE-2020-26870
- Severity: medium (CVSS 6.1 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 4.9% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2020-10-07 · updated 2026-06-17
- Weakness: CWE-79
Description
Cure53 DOMPurify before 2.0.17 allows mutation XSS. This occurs because a serialize-parse roundtrip does not necessarily return the original DOM tree, and a namespace can change from HTML to MathML, as demonstrated by nesting of FORM elements.
Affected products
- cure53 DOMPurify: before 2.0.17 — fixed in 2.0.17
- Debian Linux: 9.0
- Microsoft Visual Studio 2017 version 15.9 (includes 15.0 - 15.8): 15.9
- Microsoft Visual Studio 2019: 16.0, 16.4, 16.7, 16.8
- Oracle Corporation Application Express: before 21.1.0.00.01 — fixed in 21.1.0.00.01
How to fix
Upgrade to a fixed version: cure53 DOMPurify 2.0.17; Oracle Corporation Application Express 21.1.0.00.01. Check the vendor advisory for mitigations.
References
- https://github.com/cure53/DOMPurify/commit/02724b8eb048dd219d6725b05c3000936f11d62d
- https://github.com/cure53/DOMPurify/compare/2.0.16...2.0.17
- https://lists.debian.org/debian-lts-announce/2020/10/msg00029.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-26870
- https://research.securitum.com/mutation-xss-via-mathml-mutation-dompurify-2-0-17-bypass/
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://github.com/cure53/DOMPurify/commit/02724b8eb048dd219d6725b05c3000936f11d62d
- https://github.com/cure53/DOMPurify/compare/2.0.16...2.0.17
- https://lists.debian.org/debian-lts-announce/2020/10/msg00029.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-26870
- https://research.securitum.com/mutation-xss-via-mathml-mutation-dompurify-2-0-17-bypass/
- https://www.oracle.com//security-alerts/cpujul2021.html
Get alerted when CVE-2020-26870 or the next vulnerability affects your stack