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TI-2020-16379 Aliases CVE-2020-26956GHSA-2rfm-q54c-ww9j

Cross-site scripting in Mozilla Firefox

Priority LOW 30CWE-79Published · Updated

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

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.

Why it matters now

EPSS 0.01233 69th 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

VendorProductAffected versionsFixed inStatusSource
MozillaFirefoxbefore 8383Patch availableCNA
MozillaFirefox ESRbefore 78.578.5Patch availableCNA
MozillaThunderbirdbefore 78.578.5Patch availableCNA
  • 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

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 83.0VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 78.5VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 78.5VulnerableMozilla
  • 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: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 5AffectedNo 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

  1. 2026-10-02 Threatist record created from CVE-2020-26956
  2. 2026-10-03 Alias added: GHSA-2rfm-q54c-ww9j

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