CVE-2020-15656

Name: CVE-2020-15656
Creator: NVD / NIST
Published: 2020-08-10T18:15:12.547+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 1.51%

Last modified Jun 17, 2026

CVE-2020-15656 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. JIT optimizations involving the Javascript arguments object could confuse later optimizations. This risk was already mitigated by various precautions in the code, resulting in this bug rated at only moderate severity. EPSS estimates a 1.51% chance of exploitation in the next 30 days.

Description

JIT optimizations involving the Javascript arguments object could confuse later optimizations. This risk was already mitigated by various precautions in the code, resulting in this bug rated at only moderate severity. This vulnerability affects Firefox ESR < 78.1, Firefox < 79, and Thunderbird < 78.1.

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

1.51%

71.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-843

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 79.0
Mozilla	Firefox Esr	< 78.1
Mozilla	Thunderbird	< 78.1
Opensuse	Leap	15.2
Canonical	Ubuntu Linux	16.04
Canonical	Ubuntu Linux	18.04
Canonical	Ubuntu Linux	20.04

References

http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00025.htmlThird Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1647293Issue Tracking, Permissions Required, Vendor Advisory
https://usn.ubuntu.com/4443-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-30/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-32/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-33/Vendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00025.htmlThird Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1647293Issue Tracking, Permissions Required, Vendor Advisory
https://usn.ubuntu.com/4443-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-30/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-32/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-33/Vendor Advisory

Timeline

Published: Aug 10, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-15656?

How severe is CVE-2020-15656?

CVE-2020-15656 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 1.51% probability of exploitation in the next 30 days.

How do I fix CVE-2020-15656?

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-2020-15656?

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

Scan your code now

Source: NVD / NIST