What’s Vulnerable › Vulnerabilities

CVE-2020-15656

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-08-10 · updated 2026-06-17
• Weakness: CWE-843

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.

Affected products

• Canonical Ubuntu Linux: 16.04, 18.04, 20.04
• Mozilla Firefox: before 79.0 — fixed in 79.0
• Mozilla Firefox ESR: before 78.1 — fixed in 78.1
• Mozilla Thunderbird: before 78.1 — fixed in 78.1
• openSUSE Leap: 15.2

How to fix

Upgrade to a fixed version: Mozilla Firefox 79.0; Mozilla Firefox ESR 78.1; Mozilla Thunderbird 78.1. Check the vendor advisory for mitigations.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00025.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1647293
• https://usn.ubuntu.com/4443-1/
• https://www.mozilla.org/security/advisories/mfsa2020-30/
• https://www.mozilla.org/security/advisories/mfsa2020-32/
• https://www.mozilla.org/security/advisories/mfsa2020-33/
• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00025.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1647293
• https://usn.ubuntu.com/4443-1/
• https://www.mozilla.org/security/advisories/mfsa2020-30/
• https://www.mozilla.org/security/advisories/mfsa2020-32/
• https://www.mozilla.org/security/advisories/mfsa2020-33/

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