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TI-2021-16096 Aliases CVE-2021-38496GHSA-3rfx-pjp7-cvfp

Use after free in Mozilla Thunderbird

Priority MEDIUM 41CWE-416Published · 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-416 and the CVSS impact.

Summary

During operations on MessageTasks, a task may have been removed while it was still scheduled, resulting in memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.15, Thunderbird < 91.2, Firefox ESR < 91.2, Firefox ESR < 78.15, and Firefox < 93.

Why it matters now

EPSS 0.01659 76th percentileScored 2026-11-07
Fix Partial Thunderbird (Mozilla): 78.15, 91.2Firefox ESR (Mozilla): 91.2, 78.15+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
MozillaThunderbirdbefore 78.15; before 91.278.15, 91.2Patch availableCNA
MozillaFirefox ESRbefore 91.2; before 78.1591.2, 78.15Patch availableCNA
MozillaFirefoxbefore 9393Patch availableCNA
  • Thunderbird VendorMozilla Affected before 78.15; before 91.2 Fixed in 78.15, 91.2 Patch available CNA
  • Firefox ESR VendorMozilla Affected before 91.2; before 78.15 Fixed in 91.2, 78.15 Patch available CNA
  • Firefox VendorMozilla Affected before 93 Fixed in 93 Patch available CNA

CPE configurations NVD · 6

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 93.0; 91.0 to before 91.2VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 78.15VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 78.15; 91.0 to before 91.2VulnerableMozilla
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*9.0VulnerableDebian
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*10.0VulnerableDebian
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*11.0VulnerableDebian
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 93.0; 91.0 to before 91.2 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 78.15 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.15; 91.0 to before 91.2 Vulnerable ·Mozilla
  • cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Debian
  • cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
  • cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* Versions 11.0 Vulnerable ·Debian

Remediation

  • Fix · CNA Thunderbird (Mozilla) Fixed in 78.15, 91.2
  • Fix · CNA Firefox ESR (Mozilla) Fixed in 91.2, 78.15
  • Fix · CNA Firefox (Mozilla) Fixed in 93

Red Hat 8 advisories

  • RHSA-2021:3841 Released 2021-10-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-91.2.0-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-91.2.0-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-91.2.0-1.el7_9
  • RHSA-2021:3838 Released 2021-10-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-91.2.0-1.el8_4
  • RHSA-2021:3839 Released 2021-10-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-91.2.0-1.el8_2
Show 5 more Red Hat advisories
  • RHSA-2021:3840 Released 2021-10-13 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-91.2.0-1.el8_1
  • RHSA-2021:3791 Released 2021-10-12 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux Client (v. 7) firefox-91.2.0-4.el7_9
    • Red Hat Enterprise Linux Client Optional (v. 7) firefox-91.2.0-4.el7_9
    • Red Hat Enterprise Linux Server (v. 7) firefox-91.2.0-4.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) firefox-91.2.0-4.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) firefox-91.2.0-4.el7_9
    • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-91.2.0-4.el7_9
  • RHSA-2021:3755 Released 2021-10-11 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-91.2.0-4.el8_4
  • RHSA-2021:3757 Released 2021-10-11 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox-91.2.0-4.el8_1
  • RHSA-2021:3756 Released 2021-10-11 · Red Hat rating Important
    firefox security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox-91.2.0-4.el8_2

Fixed in the same release

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

  • Release ·

    Mozilla Firefox 93

    6 records Highest priority Priority MEDIUM 4 MEDIUM, 2 LOW

    Other records, highest priority first

    • TI-2021-16100 Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1.Priority MEDIUM 41
    • TI-2021-16101 Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1.Priority MEDIUM 40
    • TI-2021-16099 Out-of-bounds write in Mozilla FirefoxPriority MEDIUM 40
    Show all 6 records →
  • Release ·

    Mozilla Firefox ESR, Thunderbird 78.15, 91.2

    2 records Highest priority Priority MEDIUM 2 MEDIUM

    Other records, highest priority first

    • TI-2021-16100 Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1.Priority MEDIUM 41
    Show all 2 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-2021:3755, RHSA-2021:3838
Red Hat Enterprise Linux AppStream EUS (v. 8.1)Fixed RHSA-2021:3757, RHSA-2021:3840
Red Hat Enterprise Linux AppStream EUS (v. 8.2)Fixed RHSA-2021:3756, RHSA-2021:3839
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2021:3791, RHSA-2021:3841
Red Hat Enterprise Linux Client Optional (v. 7)Fixed RHSA-2021:3791
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2021:3791
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2021:3791, RHSA-2021:3841
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2021:3791, RHSA-2021:3841
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2021:3791

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-38496
  2. 2026-10-03 Alias added: GHSA-3rfx-pjp7-cvfp

References

Advisory 7

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