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Fencer Vulns
high 8.8

CVE-2021-38495 json

Mozilla developers reported memory safety bugs present in Thunderbird 78.13.0.

published 2021-11-03 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-24947

cvss
8.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 66%
public exploits
0
none known

Summary

Mozilla developers reported memory safety bugs present in Thunderbird 78.13.0. 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 Thunderbird < 91.1 and Firefox ESR < 91.1.

Patch / fix

  • Mozilla Thunderbird 91.1
  • Mozilla Firefox ESR 91.1
  • thunderbird Ubuntu 18.04 LTS 1:91.5.0+build1-0ubuntu0.18.04.1
  • thunderbird Ubuntu 20.04 LTS 1:91.5.0+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2021-38495

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 91.9.0-112.104.1
  • MozillaFirefox SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 91.9.0-150000.150.34.1
  • MozillaThunderbird SLE Workstation Extension 15 SP3, SLE Workstation Extension 15 SP2 91.4.0-8.45.2
  • MozillaFirefox SLE Module for Desktop Applications 15 SP3, SLE Module for Desktop Applications 15 SP2 91.2.0-8.54.1
  • MozillaFirefox-branding-SLE SLE Module for Desktop Applications 15 SP3, SLE Module for Desktop Applications 15 SP2 91-9.5.1
  • MozillaFirefox SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 91.2.0-3.155.2
  • MozillaFirefox-branding-SLE SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 91-4.19.1
  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 91.1.0-112.71.1

suse advisories SUSE-SU-2022:1582-1SUSE-SU-2022:1577-1SUSE-SU-2021:4150-1SUSE-SU-2021:14826-1SUSE-SU-2021:3451-1SUSE-SU-2021:3331-1

  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird openSUSE Leap 15.2 91.4.0-lp152.2.52.1
  • MozillaThunderbird openSUSE Leap 15.3 91.4.0-8.45.2
  • MozillaFirefox openSUSE Leap 15.2 91.2.0-lp152.2.67.1
  • rust-cbindgen openSUSE Leap 15.2 0.19.0-lp152.2.7.1
  • MozillaFirefox openSUSE Leap 15.3 91.2.0-8.54.1
  • MozillaFirefox-branding-SLE openSUSE Leap 15.3 91-9.5.1
  • rust-cbindgen openSUSE Leap 15.3 0.19.0-1.9.1

opensuse advisories openSUSE-SU-2024:10601-1openSUSE-SU-2021:1635-1openSUSE-SU-2021:4150-1openSUSE-SU-2021:1367-1openSUSE-SU-2021:3451-1openSUSE-SU-2021:3331-1

  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +6 more 91.2.0-r0
  • thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 91.3.2-r0

alpine advisories ALPINE-CVE-2021-38495

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • thunderbird Arch Linux 91.1.0-1

arch linux advisories AVG-2291

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-38495 updated cvss 7.5

Mozilla: Memory safety bugs fixed in Firefox 92 and Firefox ESR 91.1

  • Red Hat Enterprise Linux 6 firefox Red Hat Enterprise Linux 7 firefox Red Hat Enterprise Linux 8 firefox
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.11% chance of exploitation in the next 30 days, higher than 66% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla Thunderbird
  • Mozilla Firefox ESR

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.