CVEvulnerability

CVE-2020-6820

8.1 HIGH Known exploited Published 2020-04-24 Modified 2026-06-17 Official page ↗

CISA Known Exploited Vulnerability

Mozilla Firefox And Thunderbird Use-After-Free Vulnerability — Mozilla Firefox and Thunderbird

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.

Added to KEV
2021-11-03
Remediation due
2022-05-03
Ransomware use
Unknown
Required action
Apply updates per vendor instructions.
Notes
https://nvd.nist.gov/vuln/detail/CVE-2020-6820
Status
Analyzed
Published
2020-04-24
Last modified
2026-06-17
Assigner
[email protected]
CVSS 3.1 ([email protected])
8.1 HIGH — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1 (134c704f-9b21-4f2e-91b3-4a467353bcc0)
8.1 HIGH — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0 ([email protected])
6.8 MEDIUM — AV:N/AC:M/Au:N/C:P/I:P/A:P
Weaknesses
CWE-362

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 configurations

• mozilla firefox (< 68.6.1) • mozilla firefox (< 74.0.1) • mozilla thunderbird (< 68.7.0)

Related

Weakness · CWE (1)

  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization weakness

References