CVE-2020-6820

HighCVSS 8.1/10Known exploited (CISA KEV)Last modified Jun 17, 2026

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.

Metrics

CVSS 3.1 8.1/10CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness enumeration

CWE-362

Affected software

No affected versions have been published.

Timeline

Published: Apr 24, 2020
Last modified: Jun 17, 2026
Added to CISA KEV: Nov 3, 2021
NVD status: Analyzed

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