CVE-2020-26974

Name: CVE-2020-26974
Creator: NVD / NIST
Published: 2021-01-07T14:15:12+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 1.47%

Last modified Jun 17, 2026

CVE-2020-26974 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. When flex-basis was used on a table wrapper, a StyleGenericFlexBasis object could have been incorrectly cast to the wrong type. This resulted in a heap user-after-free, memory corruption, and a potentially exploitable crash. EPSS estimates a 1.47% chance of exploitation in the next 30 days.

Description

When flex-basis was used on a table wrapper, a StyleGenericFlexBasis object could have been incorrectly cast to the wrong type. This resulted in a heap user-after-free, memory corruption, and a potentially exploitable crash. This vulnerability affects Firefox < 84, Thunderbird < 78.6, and Firefox ESR < 78.6.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

1.47%

70.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 84.0
Mozilla	Firefox Esr	< 78.6.0
Mozilla	Thunderbird	< 78.6.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1681022Permissions Required
https://www.mozilla.org/security/advisories/mfsa2020-54/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-55/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-56/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1681022Permissions Required
https://www.mozilla.org/security/advisories/mfsa2020-54/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-55/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-56/Vendor Advisory

Timeline

Published: Jan 7, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-26974?

How severe is CVE-2020-26974?

CVE-2020-26974 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 1.47% probability of exploitation in the next 30 days.

How do I fix CVE-2020-26974?

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-2020-26974?

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

Scan your code now

Source: NVD / NIST