Live › vulnerability › CVE-2020-6820
Go to dashboardMozilla Firefox and Thunderbird have a race condition in how they handle a ReadableStream, which leads to a use-after-free memory bug. The sources say the impact is unspecified, but the bug is listed as actively exploited in the wild.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 19:11 UTC, 3h before NVD. All times on this page are UTC.
Apply updates per vendor instructions.
| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| Mozilla Firefox and Thunderbird | vendor | – | – |
Check the installed Firefox or Thunderbird version under Help > About; unknown for command-line checks.
Update Firefox and Thunderbird to the current vendor release, as CISA directs (apply updates per vendor instructions); unknown for exact fixed version.
Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
Mozilla Firefox and Thunderbird contain a race condition vulnerability when handling a ReadableStream under certain conditions. The race condition creates a use-after-free vulnerability, causing unspecified impacts.
CISA required action: Apply updates per vendor instructions.
This page as .md · .json · in your agent: get_signal("CVE-2020-6820")
CISA KEV catalog, Creative Commons 0 · EPSS scores by FIRST, used with attribution · NVD data is provided by NIST and is public domain. Posts quoted belong to their authors.