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Fencer Vulns
high 8.8

CVE-2020-15663 json

If Firefox is installed to a user-writable directory, the Mozilla Maintenance Service would execute updater.exe from the install location w…

published 2020-10-01 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-7650

cvss
8.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.7%
EPSS 2.7% chance of exploitation in 30 days, percentile 86%
public exploits
0
none known

Summary

If Firefox is installed to a user-writable directory, the Mozilla Maintenance Service would execute updater.exe from the install location with system privileges. Although the Mozilla Maintenance Service does ensure that updater.exe is signed by Mozilla, the version could have been rolled back to a previous version which would have allowed exploitation of an older bug and arbitrary code execution with System Privileges. *Note: This issue only affected Windows operating systems. Other operating systems are unaffected.*. This vulnerability affects Firefox < 80, Thunderbird < 78.2, Thunderbird < 68.12, Firefox ESR < 68.12, and Firefox ESR < 78.2.

Patch / fix

  • Mozilla Firefox 80
  • Mozilla Thunderbird 68.12, 78.2
  • Mozilla Firefox ESR 68.12, 78.2
  • MozillaFirefox SLE Module for Desktop Applications 15 SP2 78.3.0-8.6.1
  • MozillaFirefox SLE Module for Desktop Applications 15 SP1 78.2.0-3.105.1
  • MozillaThunderbird SLE Workstation Extension 15 SP2, SLE Workstation Extension 15 SP1 68.12.0-3.94.1
  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 78.2.0-112.19.2
  • MozillaFirefox SLES 11 SP4-LTSS 78.2.0-78.90.2

suse advisories SUSE-SU-2020:2749-1SUSE-SU-2020:14489-1SUSE-SU-2020:2563-1SUSE-SU-2020:2552-1SUSE-SU-2020:2544-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2
  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird openSUSE Leap 15.2 68.12.0-lp152.2.10.1
  • MozillaFirefox openSUSE Leap 15.2 78.2.0-lp152.2.18.1
  • MozillaFirefox openSUSE Leap 15.1 78.2.0-lp151.2.65.1
  • MozillaThunderbird openSUSE Leap 15.1 68.12.0-lp151.2.50.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1openSUSE-SU-2024:10601-1openSUSE-SU-2020:1392-1openSUSE-SU-2020:1391-1openSUSE-SU-2020:1384-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 80.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 80.0-r0
  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 78.2.0-r0

alpine advisories ALPINE-CVE-2020-15663

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

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-2020-15663 updated cvss 8.8

Mozilla: Downgrade attack on the Mozilla Maintenance Service could have resulted in escalation of privilege

  • Red Hat Enterprise Linux 5 firefox, thunderbird Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 firefox, thunderbird Red Hat Enterprise Linux 8 firefox, thunderbird
    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

2.72% chance of exploitation in the next 30 days, higher than 86% 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 9.3 AV:N/AC:M/Au:N/C:C/I:C/A:C

Affected products

  • Mozilla Firefox
  • Mozilla Thunderbird
  • Mozilla Firefox ESR

Classification

Weakness
  • CWE-427 Uncontrolled Search Path Element

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.