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TI-2021-16093 Aliases CVE-2021-38493GHSA-6rrw-rx8w-qx97

Out-of-bounds write in Mozilla Firefox ESR

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: 9 fixed, 1 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

Mozilla developers reported memory safety bugs present in Firefox 91 and Firefox ESR 78.13. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 78.14, Thunderbird < 78.14, and Firefox < 92.

Why it matters now

EPSS 0.01245 69th percentileScored 2026-11-07
Fix Partial Firefox ESR (Mozilla): 78.14Thunderbird (Mozilla): 78.14+1 more productRed Hat: 8 advisoriesRed Hat: 9 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
MozillaFirefox ESRbefore 78.1478.14Patch availableCNA
MozillaThunderbirdbefore 78.1478.14Patch availableCNA
MozillaFirefoxbefore 9292Patch availableCNA
  • Firefox ESR VendorMozilla Affected before 78.14 Fixed in 78.14 Patch available CNA
  • Thunderbird VendorMozilla Affected before 78.14 Fixed in 78.14 Patch available CNA
  • Firefox VendorMozilla Affected before 92 Fixed in 92 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 92.0VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 78.14VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 78.14VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 92.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 78.14 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.14 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Firefox ESR (Mozilla) Fixed in 78.14
  • Fix · CNA Thunderbird (Mozilla) Fixed in 78.14
  • Fix · CNA Firefox (Mozilla) Fixed in 92

Red Hat 8 advisories

  • RHSA-2021:3498 Released 2021-09-13 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Client (v. 7) firefox-78.14.0-1.el7_9
    • Red Hat Enterprise Linux Client Optional (v. 7) firefox-78.14.0-1.el7_9
    • Red Hat Enterprise Linux Server (v. 7) firefox-78.14.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) firefox-78.14.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) firefox-78.14.0-1.el7_9
    • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-78.14.0-1.el7_9
  • RHSA-2021:3499 Released 2021-09-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-78.14.0-1.el8_4
  • RHSA-2021:3500 Released 2021-09-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-78.14.0-1.el8_2
Show 5 more Red Hat advisories
  • RHSA-2021:3497 Released 2021-09-13 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-78.14.0-1.el8_4
  • RHSA-2021:3496 Released 2021-09-13 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-78.14.0-1.el8_2
  • RHSA-2021:3494 Released 2021-09-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-78.14.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-78.14.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-78.14.0-1.el7_9
  • RHSA-2021:3501 Released 2021-09-13 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox-78.14.0-1.el8_1
  • RHSA-2021:3495 Released 2021-09-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-78.14.0-1.el8_1

Fixed in the same release

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

  • Release ·

    Mozilla Firefox 92

    5 records Highest priority Priority MEDIUM 2 MEDIUM, 3 LOW

    Other records, highest priority first

    • TI-2021-16094 Out-of-bounds write in Mozilla FirefoxPriority MEDIUM 40
    • TI-2021-10609 Firefox for Android allowed navigations through the `intent://` protocol, which could be…Priority LOW 37
    • TI-2021-16092 When delegating navigations to the operating system, Firefox would accept the `mk` scheme…Priority LOW 31
    Show all 5 records →

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2021:3497, RHSA-2021:3499
Red Hat Enterprise Linux AppStream EUS (v. 8.1)Fixed RHSA-2021:3495, RHSA-2021:3501
Red Hat Enterprise Linux AppStream EUS (v. 8.2)Fixed RHSA-2021:3496, RHSA-2021:3500
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2021:3494, RHSA-2021:3498
Red Hat Enterprise Linux Client Optional (v. 7)Fixed RHSA-2021:3498
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2021:3498
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2021:3494, RHSA-2021:3498
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2021:3494, RHSA-2021:3498
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2021:3498

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-38493
  2. 2026-10-03 Alias added: GHSA-6rrw-rx8w-qx97

References

Advisory 6

  • 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