Attacker Value
Unknown
(1 user assessed)
Exploitability
Unknown
(1 user assessed)
User Interaction
Required
Privileges Required
None
Attack Vector
Network
1

CVE-2020-26951

Disclosure Date: December 09, 2020
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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.

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2
Technical Analysis

Mozilla recently announced a fix for this vulnerability in Firefox 83. They marked this as Impact: high and provided the following details in their published advisory:

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.

The ability to bypass sanitization sounds like it’s worth Firefox users to patch to version 83.

CVSS V3 Severity and Metrics
Base Score:
6.1 Medium
Impact Score:
2.7
Exploitability Score:
2.8
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack Vector (AV):
Network
Attack Complexity (AC):
Low
Privileges Required (PR):
None
User Interaction (UI):
Required
Scope (S):
Changed
Confidentiality (C):
Low
Integrity (I):
Low
Availability (A):
None

General Information

Vendors

  • Mozilla

Products

  • Firefox,
  • Firefox ESR,
  • Thunderbird

Additional Info

Technical Analysis