CVE-2020-6821: High severity Mozilla Firefox vulnerability

Published Apr 7, 2020
·
Updated

Last updated 25 August 2025

Other sources

When reading from areas partially or fully outside the source resource with WebGL's <code>copyTexSubImage</code> method, the specification requires the returned values be zero. Previously, this memory was uninitialized, leading to potentially sensitive data disclosure. This vulnerability affects Thunderbird < 68.7.0, Firefox ESR < 68.7, and Firefox < 75.

— Launchpad

When reading from areas partially or fully outside the source resource with WebGL's copyTexSubImage method, the specification requires the returned values be zero. Previously, this memory was uninitialized, leading to potentially sensitive data disclosure.

Affected Software

9 affected componentsFixes available
Mozilla Firefox<75
75
Mozilla Thunderbird<68.7
68.7
Mozilla Firefox<75.0
Mozilla Firefox ESR<68.7.0
Mozilla Thunderbird<68.7.0
Mozilla Firefox ESR<68.7
68.7
debian/firefox
152.0.6-1
debian/firefox-esr
115.14.0esr-1~deb11u1140.13.0esr-1~deb11u1140.12.0esr-1~deb12u1140.13.0esr-1~deb12u1140.12.0esr-1~deb13u1140.13.0esr-1~deb13u1140.12.0esr-1140.13.0esr-2
debian/thunderbird
1:115.12.0-1~deb11u11:140.12.0esr-1~deb11u11:140.12.0esr-1~deb12u11:140.12.0esr-1~deb13u11:140.12.0esr-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade Firefox to a version that resolves this vulnerability.

    Fixed in 75
  2. Upgrade

    Upgrade Thunderbird to a version that resolves this vulnerability.

    Fixed in 68.7
  3. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 68.7
  4. Upgrade

    Upgrade debian/firefox to a version that resolves this vulnerability.

    Fixed in 152.0.6-1
  5. Upgrade

    Upgrade debian/firefox-esr to a version that resolves this vulnerability.

    Fixed in 115.14.0esr-1~deb11u1Fixed in 140.13.0esr-1~deb11u1Fixed in 140.12.0esr-1~deb12u1Fixed in 140.13.0esr-1~deb12u1Fixed in 140.12.0esr-1~deb13u1Fixed in 140.13.0esr-1~deb13u1Fixed in 140.12.0esr-1Fixed in 140.13.0esr-2
  6. Upgrade

    Upgrade debian/thunderbird to a version that resolves this vulnerability.

    Fixed in 1:115.12.0-1~deb11u1Fixed in 1:140.12.0esr-1~deb11u1Fixed in 1:140.12.0esr-1~deb12u1Fixed in 1:140.12.0esr-1~deb13u1Fixed in 1:140.12.0esr-1
  7. Upgrade

    Upgrade Mozilla Thunderbird to a version that resolves this vulnerability.

    Fixed in 68.7.0
  8. Upgrade

    Upgrade Mozilla Firefox ESR to a version that resolves this vulnerability.

    Fixed in 68.7
  9. Upgrade

    Upgrade Mozilla Firefox to a version that resolves this vulnerability.

    Fixed in 75

Event History

Apr 7, 2020
CVE Published
12:00 AM
Apr 24, 2020
CVE Published
via MITRE·03:55 PM
Data Sourced
via MITRE·03:55 PM
DescriptionWeakness
Data Sourced
via NVD·04:15 PM
DescriptionSeverityWeaknessAffected Software
Jan 11, 2024
Data Sourced
via Launchpad·11:52 PM
Description
Feb 23, 2026
Data Sourced
via Ubuntu·03:19 PM
RemedyDescriptionSeverityAffected Software
Jul 24, 2026
Data Sourced
via Debian·04:21 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is CVE-2020-6821?

CVE-2020-6821 is a vulnerability in Mozilla Firefox and Thunderbird that allows potential sensitive data disclosure when reading from areas outside the source resource with WebGL's copyTexSubImage method.

2

Which software is affected by CVE-2020-6821?

Mozilla Firefox (up to version 75.0), Mozilla Firefox ESR (up to version 68.7.0), and Mozilla Thunderbird (up to version 68.7.0) are affected by CVE-2020-6821.

3

How severe is CVE-2020-6821?

CVE-2020-6821 has a severity rating of high.

4

How can I fix CVE-2020-6821?

Update your Mozilla Firefox or Thunderbird to the latest version available to mitigate CVE-2020-6821.

5

Where can I find more information about CVE-2020-6821?

You can find more information about CVE-2020-6821 on Mozilla's security advisories and the MITRE CVE database.

Company

Resources

Contact

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