CVE-2020-26870

Exp

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.

Published: 2020-10-07 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]

NVD Status：Modified，CVE State: published

View at NVD, CVE.org, EUVD

Threat Intelligence & Risk Assessment for CVE-2020-26870

EPSS CVSS CWE GHSA Exploit-DB Affected OS Tracker

Conclusion & alert: CVE-2020-26870 is rated High Exploit Risk (75.1/100): CVSS Medium severity, with high exploitation likelihood (EPSS 4.52%, 90th percentile). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +4.11% over the last day, indicating growing attacker interest. Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2020-26870

EDB-ID	Source	Kind	Published	Link
—	nvd_ref	exploit_tag		Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2020-26870

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.42%	4.52%	+4.11%
2	2026-03-04	0.31%	0.42%	+0.11%
3	2026-03-01	—	0.31%	—

Full EPSS history (41 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-26870

CVSS metrics for this CVE.

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
6.1	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	2.8	2.7	[email protected]
4.3	2.0	MEDIUM	`AV:N/AC:M/Au:N/C:N/I:P/A:N` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:M) Exploitation needs some favorable conditions, but not exceptional ones. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:N) No availability impact.	8.6	2.9	[email protected]

Weakness enumeration for CVE-2020-26870

CWE-79 MITRE ↗

GitHub Security Advisory for CVE-2020-26870

GHSA-63q7-h895-m982 · Severity: medium · Ecosystem: npm — Cross-site Scripting in dompurify

OS Trackers for CVE-2020-26870

vendor	priority	summary	link
`ubuntu`	low	CVE-2020-26870 low priority: Ubuntu including 1 source packages (dompurify.js), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 13, needs-triage 3.	https://ubuntu.com/security/CVE-2020-26870

Affected software / configurations for CVE-2020-26870

Vendor	Product	Version	Raw CPE
cure53	dompurify	< 2.0.17	cpe:2.3:a:cure53:dompurify::::::::
debian	debian_linux	9.0	cpe:2.3:o:debian:debian_linux:9.0:::::::*
microsoft	visual_studio_2017	15.9	cpe:2.3:a:microsoft:visual_studio_2017:15.9:::::::*
microsoft	visual_studio_2019	16.0	cpe:2.3:a:microsoft:visual_studio_2019:16.0:::::::*
microsoft	visual_studio_2019	16.4	cpe:2.3:a:microsoft:visual_studio_2019:16.4:::::::*
microsoft	visual_studio_2019	16.7	cpe:2.3:a:microsoft:visual_studio_2019:16.7:::::::*
microsoft	visual_studio_2019	16.8	cpe:2.3:a:microsoft:visual_studio_2019:16.8:::::::*
oracle	application_express	< 21.1.0.00.01	cpe:2.3:a:oracle:application_express::::::::

References for CVE-2020-26870

URL	Tags
https://github.com/cure53/DOMPurify/commit/02724b8eb048dd219d6725b05c3000936f11d62d	Patch Third Party Advisory
https://github.com/cure53/DOMPurify/compare/2.0.16...2.0.17	Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00029.html	Mailing List Third Party Advisory
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-26870	Patch 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.html	Patch Third Party Advisory

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