Is CVE-2020-26956 in the CISA KEV catalog?

No. CVE-2020-26956 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2020-26956?

CVE-2020-26956 has a CVSS v3 base score of 6.1 (MEDIUM).

What is the EPSS score for CVE-2020-26956?

CVE-2020-26956 has an EPSS score of 1.22% (65th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2020-26956?

Upgrade firefox on debian unstable to 83.0-1 or later. Fixes are available for 6 affected products.

CVE & CISA-KEV Catalog

CVE-2020-26956

MEDIUM

6.1

CVSS v3

NVD

Description

In some cases, removing HTML elements during sanitization would keep existing SVG event handlers and therefore lead to XSS. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.

CWE-79Cross-Site Scripting (XSS)

How to fix

Remediation Available

firefoxDebian

Fixed in:83.0-1CVE-2020-26956

firefoxUbuntu

Fixed in:83.0+build2-0ubuntu0.16.04.3USN-4637-2

Fixed in:83.0+build2-0ubuntu0.18.04.2USN-4637-1

Fixed in:83.0+build2-0ubuntu0.20.04.1USN-4637-1

DeveloperEditionWindows application

Affected:83.0Fixed in:83.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:83.0Fixed in:83.0Mozilla

Mozilla Firefox ESR (en-US)Windows application

Affected:78.5Fixed in:78.5Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:78.5Fixed in:78.5Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeChanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

1.22%probability of exploitation in 30 days

65thpercentile

Moderate risk: more likely to be exploited than 65% of all known CVEs.

References

Vendor Advisory4

Related Vulnerabilities

Other CWE-79 (Cross-Site Scripting (XSS)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-11022	Medium	6.9	99%	-	Fix
CVE-2019-3929	Critical	9.8	99%	KEV	Fix
CVE-2020-9496	Medium	6.1	99%	-	-
CVE-2023-28341	Medium	6.1	99%	-	Fix
CVE-2018-12998	Medium	6.1	98%	-	-
CVE-2025-4123	High	7.6	98%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.