CVE-2020-15663

Name: CVE-2020-15663
Creator: NVD / NIST
Published: 2020-10-01T19:15:12.97+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 2.60%

Last modified Jun 17, 2026

CVE-2020-15663 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. 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. EPSS estimates a 2.60% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Probability

2.60%

83.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-427

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 80.0
Mozilla	Firefox	>= 78.0, < 78.2
Mozilla	Firefox Esr	>= 68.0, < 68.12
Mozilla	Thunderbird	>= 68.0, < 68.12
Mozilla	Thunderbird	>= 78.0, < 78.2

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1643199Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-36/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-37/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-38/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-40/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-41/Release Notes, Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1643199Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-36/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-37/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-38/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-40/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-41/Release Notes, Vendor Advisory

Timeline

Published: Oct 1, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-15663?

How severe is CVE-2020-15663?

CVE-2020-15663 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 2.60% probability of exploitation in the next 30 days.

How do I fix CVE-2020-15663?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-15663?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST