CVE-2020-6821

Name: CVE-2020-6821
Creator: NVD / NIST
Published: 2020-04-24T16:15:13.51+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.47%

Last modified Jun 17, 2026

CVE-2020-6821 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 1.47% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.47%

70.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-908

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 75.0
Mozilla	Firefox Esr	< 68.7.0
Mozilla	Thunderbird	< 68.7.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1625404Issue Tracking, Permissions Required
https://usn.ubuntu.com/4335-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-12/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-13/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-14/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1625404Issue Tracking, Permissions Required
https://usn.ubuntu.com/4335-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-12/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-13/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-14/Vendor Advisory

Timeline

Published: Apr 24, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-6821?

How severe is CVE-2020-6821?

CVE-2020-6821 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.47% probability of exploitation in the next 30 days.

How do I fix CVE-2020-6821?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-6821?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST