What’s Vulnerable › Vulnerabilities

CVE-2020-12420

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-07-09 · updated 2026-06-17
• Weakness: CWE-362

Description

When trying to connect to a STUN server, a race condition could have caused a use-after-free of a pointer, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox ESR < 68.10, Firefox < 78, and Thunderbird < 68.10.0.

Affected products

• Canonical Ubuntu Linux: 16.04, 18.04, 19.10, 20.04
• Mozilla Firefox: before 78.0 — fixed in 78.0
• Mozilla Firefox ESR: before 68.10.0 — fixed in 68.10.0
• Mozilla Thunderbird: before 68.10.0 — fixed in 68.10.0
• openSUSE Leap: 15.1, 15.2

How to fix

Upgrade to a fixed version: Mozilla Firefox 78.0; Mozilla Firefox ESR 68.10.0; Mozilla Thunderbird 68.10.0. Check the vendor advisory for mitigations.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00023.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00026.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1643437
• https://security.gentoo.org/glsa/202007-09
• https://security.gentoo.org/glsa/202007-10
• https://usn.ubuntu.com/4421-1/
• https://www.mozilla.org/security/advisories/mfsa2020-24/
• https://www.mozilla.org/security/advisories/mfsa2020-25/
• https://www.mozilla.org/security/advisories/mfsa2020-26/
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00023.html

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