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CVE-2020-26951

MEDIUM
6.1
CVSS Score
Published: December 9, 2020 at 12:19 AM UTC
Updated: June 17, 2026 at 03:08 AM UTC
3 products affected across 1 vendorFirefoxThunderbirdFirefox ESR

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Severity
MEDIUM6.1
Exploit prediction
EPSS 1%

Description

A parsing and event loading mismatch in Firefox's SVG code could have allowed load events to fire, even after sanitization. An attacker already capable of exploiting an XSS vulnerability in privileged internal pages could have used this attack to bypass our built-in sanitizer. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Firefox· Mozilla
95%
v < 83
Affected range stops below 83, so it looks safe — our inference, not a vendor statement
Affected range stops below 83.0, so it looks safe — our inference, not a vendor statement
Firefox ESR· Mozilla
95%
v < 78.5
Affected range stops below 78.5, so it looks safe — our inference, not a vendor statement
Thunderbird· Mozilla
95%
v < 78.5
Affected range stops below 78.5, so it looks safe — our inference, not a vendor statement

References (4)

x_refsource_MISCIssue TrackingPermissions RequiredVendor Advisory
Source: [email protected]
https://bugzilla.mozilla.org/show_bug.cgi?id=1667113
x_refsource_CONFIRMVendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2020-50/
x_refsource_CONFIRMVendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2020-51/
x_refsource_CONFIRMVendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2020-52/

CVSS

6.1MEDIUM[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-79

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