TI-2020-16374 Aliases CVE-2020-26951 GHSA-w7p8-wf2r-rw5h

Cross-site scripting in Mozilla Firefox

LOW 29CWE-79Published 2020-12-09 · Updated 2024-08-04

Key facts

Attack vector: Network
Privileges required: None
User interaction: Required
Attack complexity: Low
Impact type: Cross-site scripting
Confidentiality · integrity · availability: Low · Low · None
Fix status: Partial Red Hat: 15 fixed, 1 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-79.

Summary

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.

Why it matters now

EPSS 0.01051 64th percentileScored 2026-11-07

Fix Partial Firefox (Mozilla): 83Firefox ESR (Mozilla): 78.5+1 more productRed Hat: 12 advisoriesRed Hat: 15 fixed, 1 without a fix

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Mozilla	Firefox	before 83	83	Patch available	CNA
Mozilla	Firefox ESR	before 78.5	78.5	Patch available	CNA
Mozilla	Thunderbird	before 78.5	78.5	Patch available	CNA

Firefox VendorMozilla Affected before 83 Fixed in 83 Patch available CNA
Firefox ESR VendorMozilla Affected before 78.5 Fixed in 78.5 Patch available CNA
Thunderbird VendorMozilla Affected before 78.5 Fixed in 78.5 Patch available CNA

CPE configurations NVD · 3

CPE	Versions	Role	Vendor
cpe:2.3:a:mozilla:firefox::::::::	before 83.0	Vulnerable	Mozilla
cpe:2.3:a:mozilla:firefox_esr::::::::	before 78.5	Vulnerable	Mozilla
cpe:2.3:a:mozilla:thunderbird::::::::	before 78.5	Vulnerable	Mozilla

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 83.0 Vulnerable ·Mozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 78.5 Vulnerable ·Mozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.5 Vulnerable ·Mozilla

Remediation

Fix · CNA Firefox (Mozilla) Fixed in 83
Fix · CNA Firefox ESR (Mozilla) Fixed in 78.5
Fix · CNA Thunderbird (Mozilla) Fixed in 78.5

Red Hat 12 advisories

RHSA-2020:5314 Released 2020-12-01 · Red Hat rating Important
firefox security update
- Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox-78.5.0-1.el8_0
RHSA-2020:5239 Released 2020-11-30 · Red Hat rating Important
firefox security update
- Red Hat Enterprise Linux Client (v. 7) firefox-78.5.0-1.el7_9
- Red Hat Enterprise Linux Client Optional (v. 7) firefox-78.5.0-1.el7_9
- Red Hat Enterprise Linux Server (v. 7) firefox-78.5.0-1.el7_9
- Red Hat Enterprise Linux Server Optional (v. 7) firefox-78.5.0-1.el7_9
- Red Hat Enterprise Linux Workstation (v. 7) firefox-78.5.0-1.el7_9
- Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-78.5.0-1.el7_9
RHSA-2020:5235 Released 2020-11-30 · Red Hat rating Important
thunderbird security update
- Red Hat Enterprise Linux Client (v. 7) thunderbird-78.5.0-1.el7_9
- Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-78.5.0-1.el7_9
- Red Hat Enterprise Linux Workstation (v. 7) thunderbird-78.5.0-1.el7_9

Show 9 more Red Hat advisories

RHSA-2020:5257 Released 2020-11-30 · Red Hat rating Important
firefox security update
- Red Hat Enterprise Linux Desktop (v. 6) firefox-78.5.0-1.el6_10
- Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox-78.5.0-1.el6_10
- Red Hat Enterprise Linux Server (v. 6) firefox-78.5.0-1.el6_10
- Red Hat Enterprise Linux Workstation (v. 6) firefox-78.5.0-1.el6_10
RHSA-2020:5237 Released 2020-11-30 · Red Hat rating Important
firefox security update
- Red Hat Enterprise Linux AppStream (v. 8) firefox-78.5.0-1.el8_3
RHSA-2020:5238 Released 2020-11-30 · Red Hat rating Important
thunderbird security update
- Red Hat Enterprise Linux Desktop (v. 6) thunderbird-78.5.0-1.el6_10
- Red Hat Enterprise Linux Server Optional (v. 6) thunderbird-78.5.0-1.el6_10
- Red Hat Enterprise Linux Workstation (v. 6) thunderbird-78.5.0-1.el6_10
RHSA-2020:5234 Released 2020-11-30 · Red Hat rating Important
firefox security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-78.5.0-1.el8_2
RHSA-2020:5232 Released 2020-11-30 · Red Hat rating Important
thunderbird security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-78.5.0-1.el8_2
RHSA-2020:5236 Released 2020-11-30 · Red Hat rating Important
thunderbird security update
- Red Hat Enterprise Linux AppStream (v. 8) thunderbird-78.5.0-1.el8_3
RHSA-2020:5233 Released 2020-11-30 · Red Hat rating Important
firefox security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox-78.5.0-1.el8_1
RHSA-2020:5231 Released 2020-11-30 · Red Hat rating Important
thunderbird security update
- Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-78.5.0-1.el8_1
RHSA-2020:5240 Released 2020-11-30 · Red Hat rating Important
thunderbird security update
- Red Hat Enterprise Linux AppStream E4S (v. 8.0) thunderbird-78.5.0-1.el8_0

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat Enterprise Linux 5	Affected	No fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)	Fixed	RHSA-2020:5236, RHSA-2020:5237
Red Hat Enterprise Linux AppStream E4S (v. 8.0)	Fixed	RHSA-2020:5240, RHSA-2020:5314
Red Hat Enterprise Linux AppStream EUS (v. 8.1)	Fixed	RHSA-2020:5231, RHSA-2020:5233
Red Hat Enterprise Linux AppStream EUS (v. 8.2)	Fixed	RHSA-2020:5232, RHSA-2020:5234
Red Hat Enterprise Linux Client (v. 7)	Fixed	RHSA-2020:5235, RHSA-2020:5239
Red Hat Enterprise Linux Client Optional (v. 7)	Fixed	RHSA-2020:5239
Red Hat Enterprise Linux Desktop (v. 6)	Fixed	RHSA-2020:5238, RHSA-2020:5257
Red Hat Enterprise Linux HPC Node Optional (v. 6)	Fixed	RHSA-2020:5257
Red Hat Enterprise Linux Server (v. 6)	Fixed	RHSA-2020:5257
Red Hat Enterprise Linux Server (v. 7)	Fixed	RHSA-2020:5239
Red Hat Enterprise Linux Server Optional (v. 6)	Fixed	RHSA-2020:5238
Red Hat Enterprise Linux Server Optional (v. 7)	Fixed	RHSA-2020:5235, RHSA-2020:5239
Red Hat Enterprise Linux Workstation (v. 6)	Fixed	RHSA-2020:5238, RHSA-2020:5257
Red Hat Enterprise Linux Workstation (v. 7)	Fixed	RHSA-2020:5235, RHSA-2020:5239
Red Hat Enterprise Linux Workstation Optional (v. 7)	Fixed	RHSA-2020:5239

Timeline

2026-10-02 Threatist record created from CVE-2020-26951
2026-10-03 Alias added: GHSA-w7p8-wf2r-rw5h

References

Advisory 4

TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8

See all 3444 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences