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TI-2021-16101 Aliases CVE-2021-38501GHSA-jm85-6c37-hfcj

Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1.

Priority MEDIUM 40Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
—
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.

Summary

Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1. 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 < 93, Thunderbird < 91.2, and Firefox ESR < 91.2.

Why it matters now

EPSS 0.01048 64th percentileScored 2026-11-07
Fix Partial Firefox (Mozilla): 93Thunderbird (Mozilla): 91.2+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
MozillaFirefoxbefore 9393Patch availableCNA
MozillaThunderbirdbefore 91.291.2Patch availableCNA
MozillaFirefox ESRbefore 91.291.2Patch availableCNA
  • Firefox VendorMozilla Affected before 93 Fixed in 93 Patch available CNA
  • Thunderbird VendorMozilla Affected before 91.2 Fixed in 91.2 Patch available CNA
  • Firefox ESR VendorMozilla Affected before 91.2 Fixed in 91.2 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*before 93.0VulnerableMozilla
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*before 91.2VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 91.2VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* Versions before 93.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* Versions before 91.2 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 91.2 Vulnerable ·Mozilla

Remediation

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

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-2021-16096 Use after free in Mozilla ThunderbirdPriority MEDIUM 41
    • TI-2021-16099 Out-of-bounds write in Mozilla FirefoxPriority MEDIUM 40
    Show all 6 records →
  • Release ·

    Mozilla Thunderbird 91.2

    4 records Highest priority Priority MEDIUM 1 MEDIUM, 3 LOW

    Other records, highest priority first

    • TI-2021-16098 Use after free in Mozilla FirefoxPriority LOW 36
    • TI-2021-16097 Origin validation error in Mozilla FirefoxPriority LOW 30
    • TI-2021-16102 Thunderbird ignored the configuration to require STARTTLS security for an SMTP connection.Priority LOW 29
    Show all 4 records →
Show 1 more group
  • Release ·

    Mozilla Firefox ESR 91.2

    3 records Highest priority Priority MEDIUM 1 MEDIUM, 2 LOW

    Other records, highest priority first

    • TI-2021-16098 Use after free in Mozilla FirefoxPriority LOW 36
    • TI-2021-16097 Origin validation error in Mozilla FirefoxPriority LOW 30
    Show all 3 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-2021-38501
  2. 2026-10-03 Alias added: GHSA-jm85-6c37-hfcj

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