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TI-2020-16397 Aliases CVE-2020-26974GHSA-gr4h-9jxj-93vm

Out-of-bounds write in Mozilla Firefox

Priority MEDIUM 41CWE-787Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 10 fixed, 2 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-787 and the CVSS impact.

Summary

When flex-basis was used on a table wrapper, a StyleGenericFlexBasis object could have been incorrectly cast to the wrong type. This resulted in a heap user-after-free, memory corruption, and a potentially exploitable crash. This vulnerability affects Firefox < 84, Thunderbird < 78.6, and Firefox ESR < 78.6.

Why it matters now

EPSS 0.01533 74th percentileScored 2026-11-07
Fix Partial Firefox (Mozilla): 84Thunderbird (Mozilla): 78.6+1 more productRed Hat: 10 advisoriesRed Hat: 10 fixed, 2 without a fix

SSVC decision points

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

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaFirefoxbefore 8484Patch availableCNA
MozillaThunderbirdbefore 78.678.6Patch availableCNA
MozillaFirefox ESRbefore 78.678.6Patch availableCNA
  • Firefox VendorMozilla Affected before 84 Fixed in 84 Patch available CNA
  • Thunderbird VendorMozilla Affected before 78.6 Fixed in 78.6 Patch available CNA
  • Firefox ESR VendorMozilla Affected before 78.6 Fixed in 78.6 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 84.0VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 78.6.0VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 78.6.0VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 84.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 78.6.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.6.0 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox (Mozilla) Fixed in 84
  • Fix · CNA Thunderbird (Mozilla) Fixed in 78.6
  • Fix · CNA Firefox ESR (Mozilla) Fixed in 78.6

Red Hat 10 advisories

  • RHSA-2020:5645 Released 2020-12-21 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v. 8.0) thunderbird-78.6.0-1.el8_0
  • RHSA-2020:5644 Released 2020-12-21 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-78.6.0-1.el8_1
  • RHSA-2020:5624 Released 2020-12-17 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-78.6.0-1.el8_3
Show 7 more Red Hat advisories
  • RHSA-2020:5622 Released 2020-12-17 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-78.6.0-1.el8_2
  • RHSA-2020:5618 Released 2020-12-17 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-78.6.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-78.6.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-78.6.0-1.el7_9
  • RHSA-2020:5561 Released 2020-12-16 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Client (v. 7) firefox-78.6.0-1.el7_9
    • Red Hat Enterprise Linux Client Optional (v. 7) firefox-78.6.0-1.el7_9
    • Red Hat Enterprise Linux Server (v. 7) firefox-78.6.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) firefox-78.6.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) firefox-78.6.0-1.el7_9
    • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-78.6.0-1.el7_9
  • RHSA-2020:5563 Released 2020-12-16 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-78.6.0-1.el8_2
  • RHSA-2020:5565 Released 2020-12-16 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox-78.6.0-1.el8_0
  • RHSA-2020:5562 Released 2020-12-16 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-78.6.0-1.el8_3
  • RHSA-2020:5564 Released 2020-12-16 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox-78.6.0-1.el8_1

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Mozilla Firefox 84

    13 records Highest priority Priority MEDIUM 7 MEDIUM, 6 LOW

    Other records, highest priority first

    • TI-2020-16395 Use after free in Mozilla FirefoxPriority MEDIUM 45
    • TI-2020-16394 Out-of-bounds write in Mozilla FirefoxPriority MEDIUM 42
    • TI-2020-17831 Out-of-bounds write in Mozilla FirefoxPriority MEDIUM 41
    Show all 13 records →
  • Release ·

    Mozilla Firefox ESR, Thunderbird 78.6

    7 records Highest priority Priority MEDIUM 5 MEDIUM, 2 LOW

    Other records, highest priority first

    • TI-2020-16394 Out-of-bounds write in Mozilla FirefoxPriority MEDIUM 42
    • TI-2020-17831 Out-of-bounds write in Mozilla FirefoxPriority MEDIUM 41
    • TI-2020-17830 If a user downloaded a file lacking an extension on Windows, and then "Open"-ed it from…Priority MEDIUM 41
    Show all 7 records →

Vendor assessments

Red Hat

Red Hat rating: Important. 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 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2020:5562, RHSA-2020:5624
Red Hat Enterprise Linux AppStream E4S (v. 8.0)Fixed RHSA-2020:5565, RHSA-2020:5645
Red Hat Enterprise Linux AppStream EUS (v. 8.1)Fixed RHSA-2020:5564, RHSA-2020:5644
Red Hat Enterprise Linux AppStream EUS (v. 8.2)Fixed RHSA-2020:5563, RHSA-2020:5622
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2020:5561, RHSA-2020:5618
Red Hat Enterprise Linux Client Optional (v. 7)Fixed RHSA-2020:5561
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2020:5561
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2020:5561, RHSA-2020:5618
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2020:5561, RHSA-2020:5618
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2020:5561

Timeline

  1. 2026-10-02 Threatist record created from CVE-2020-26974
  2. 2026-10-03 Alias added: GHSA-gr4h-9jxj-93vm

References

Advisory 3

Other 1

  • 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