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Actively exploited · Published Apr 24, 2020 · Assigned by mozilla

CVE-2020-6820

High 8.1 Exploited

In plain English

A high-severity race condition in Firefox from Mozilla. Attackers are actively exploiting it in the wild (listed by CISA on November 3, 2021). The chance it is exploited in the next 30 days is estimated at 7.1% (higher than 94% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.1High
Exploit odds (30 days)7.1%top 5.8% of all CVEs
Exploited in the wildYesCISA KEV since Nov 3, 2021
Attack toolingNoneno public tooling known

CISA guidance

Apply updates per vendor instructions.

Federal agencies must remediate by May 3, 2022.

Official description

Under certain conditions, when handling a ReadableStream, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20firefox74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.21firefox74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.22firefox74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.23firefox74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.20firefox-esr68.6.1-r0ALPINE-CVE-2020-6820
Alpine:v3.21firefox-esr68.6.1-r0ALPINE-CVE-2020-6820
Alpine:v3.22firefox-esr68.6.1-r0ALPINE-CVE-2020-6820
Alpine:v3.23firefox-esr68.6.1-r0ALPINE-CVE-2020-6820
Alpine:v3.21librewolf74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.22librewolf74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.23librewolf74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.24librewolf74.0.1-r0ALPINE-CVE-2020-6820
Alpine:v3.20thunderbird68.7.0-r0ALPINE-CVE-2020-6820
Alpine:v3.21thunderbird68.7.0-r0ALPINE-CVE-2020-6820
Alpine:v3.22thunderbird68.7.0-r0ALPINE-CVE-2020-6820
Alpine:v3.23thunderbird68.7.0-r0ALPINE-CVE-2020-6820
Debian:12firefox-esr68.6.1esr-1DEBIAN-CVE-2020-6820
Debian:13firefox-esr68.6.1esr-1DEBIAN-CVE-2020-6820
Debian:14firefox-esr68.6.1esr-1DEBIAN-CVE-2020-6820
Debian:12thunderbird1:68.7.0-1DEBIAN-CVE-2020-6820
Debian:13thunderbird1:68.7.0-1DEBIAN-CVE-2020-6820
Debian:14thunderbird1:68.7.0-1DEBIAN-CVE-2020-6820

Affected products (as reported)

VendorProductVersions
Mozilla Thunderbird unspecified – before 68.7.0
Mozilla Firefox unspecified – before 74.0.1
Mozilla Firefox ESR unspecified – before 68.6.1

Weakness: CWE-362 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References