CVE-2020-26870
Cross-site Scripting in dompurify
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
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.
- Record
CVE-2020-26870- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:P/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
CVE List No score
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.
- Record
CVE-2020-26870- Updated
- 2026-11-02
EUVDEUVD-2020-1486 No score
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.
- Record
EUVD-2020-1486- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-63q7-h895-m982
Cross-site Scripting in dompurify
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.
- Record
GHSA-63q7-h895-m982- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2020-26870- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVGHSA-63q7-h895-m982
Cross-site Scripting in dompurify
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.
- Record
GHSA-63q7-h895-m982- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2020-26870
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.
- Record
UBUNTU-CVE-2020-26870- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVCLSA-2026-1792601061 No score
TuxCare security update for dompurify (2 CVEs)
TuxCare rebuilt dompurify to address 2 CVEs. Fixed in 2.0.8-tuxcare.4.
- Record
CLSA-2026-1792601061- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
dompurifynpm |
before 2.0.17 | 2.0.17 |
dompurifyTuxCare:npm |
2.0.8-tuxcare.0 up to 2.0.8-tuxcare.4, plus listed versions 2.0.82.0.8-tuxcare.12.0.8-tuxcare.22.0.8-tuxcare.3 |
2.0.8-tuxcare.4 |
dompurify.jsDebian:9 |
before 0.8.2~dfsg1-1+deb9u1, plus listed versions 0.8.2~dfsg1-1 |
0.8.2~dfsg1-1+deb9u1 |
dompurify.jsUbuntu:16.04:LTS |
All versions, plus listed versions 0.7.3~dfsg1-10.7.3~dfsg1-2 |
None known |
dompurify.jsUbuntu:18.04:LTS |
All versions, plus listed versions 0.9.0~dfsg1-10.9.0~dfsg1-2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-26870 is a medium vulnerability (CVSS 6.1) in Cure53 Dompurify, published October 7, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 4.88%, the 92nd percentile. Fixed in dompurify 2.0.17.
References
research.securitum.com/mutation-xss-via-mathml-mutation-dompurify-2-0-17-bypass
github.com/cure53/DOMPurify/commit/02724b8eb048dd219d6725b05c3000936f11d62d
lists.debian.org/debian-lts-announce/2020/10/msg00029.html
portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-26870
oracle.com//security-alerts/cpujul2021.html