CVE-2020-6806

Name: CVE-2020-6806
Creator: NVD / NIST
Published: 2020-03-25T22:15:12.373+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 2.54%

Last modified Jun 17, 2026

CVE-2020-6806 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. By carefully crafting promise resolutions, it was possible to cause an out-of-bounds read off the end of an array resized during script execution. This could have led to memory corruption and a potentially exploitable crash. EPSS estimates a 2.54% chance of exploitation in the next 30 days.

Description

By carefully crafting promise resolutions, it was possible to cause an out-of-bounds read off the end of an array resized during script execution. This could have led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

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

2.54%

83.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-125

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 74.0
Mozilla	Firefox Esr	< 68.6.0
Mozilla	Thunderbird	< 68.6.0
Canonical	Ubuntu Linux	16.04
Canonical	Ubuntu Linux	18.04
Canonical	Ubuntu Linux	19.10

References

http://packetstormsecurity.com/files/157524/Firefox-js-ReadableStreamCloseInternal-Out-Of-Bounds-Access.htmlThird Party Advisory, VDB Entry
https://bugzilla.mozilla.org/show_bug.cgi?id=1612308Issue Tracking, Permissions Required
https://usn.ubuntu.com/4328-1/Third Party Advisory
https://usn.ubuntu.com/4335-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-08/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-09/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-10/Vendor Advisory
http://packetstormsecurity.com/files/157524/Firefox-js-ReadableStreamCloseInternal-Out-Of-Bounds-Access.htmlThird Party Advisory, VDB Entry
https://bugzilla.mozilla.org/show_bug.cgi?id=1612308Issue Tracking, Permissions Required
https://usn.ubuntu.com/4328-1/Third Party Advisory
https://usn.ubuntu.com/4335-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-08/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-09/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-10/Vendor Advisory

Timeline

Published: Mar 25, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-6806?

How severe is CVE-2020-6806?

CVE-2020-6806 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 2.54% probability of exploitation in the next 30 days.

How do I fix CVE-2020-6806?

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-2020-6806?

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

Scan your code now

Source: NVD / NIST