CVE-2020-26870

Name: CVE-2020-26870
Creator: NVD / NIST
Published: 2020-10-07T16:15:18.03+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 4.52%

Last modified Jun 17, 2026

CVE-2020-26870 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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.. EPSS estimates a 4.52% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

4.52%

90.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Cure53	Dompurify	< 2.0.17
Debian	Debian Linux	9.0
Microsoft	Visual Studio 2017	15.9
Microsoft	Visual Studio 2019	16.0
Microsoft	Visual Studio 2019	16.4
Microsoft	Visual Studio 2019	16.7
Microsoft	Visual Studio 2019	16.8
Oracle	Application Express	< 21.1.0.00.01

References

https://github.com/cure53/DOMPurify/commit/02724b8eb048dd219d6725b05c3000936f11d62dPatch, Third Party Advisory
https://github.com/cure53/DOMPurify/compare/2.0.16...2.0.17Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00029.htmlMailing List, Third Party Advisory
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-26870Patch, Vendor Advisory
https://research.securitum.com/mutation-xss-via-mathml-mutation-dompurify-2-0-17-bypass/Exploit, Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.htmlPatch, Third Party Advisory
https://github.com/cure53/DOMPurify/commit/02724b8eb048dd219d6725b05c3000936f11d62dPatch, Third Party Advisory
https://github.com/cure53/DOMPurify/compare/2.0.16...2.0.17Patch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00029.htmlMailing List, Third Party Advisory
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-26870Patch, Vendor Advisory
https://research.securitum.com/mutation-xss-via-mathml-mutation-dompurify-2-0-17-bypass/Exploit, Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.htmlPatch, Third Party Advisory

Timeline

Published: Oct 7, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-26870?

How severe is CVE-2020-26870?

CVE-2020-26870 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 4.52% probability of exploitation in the next 30 days.

How do I fix CVE-2020-26870?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-26870?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST