CVE-2020-26976

Name: CVE-2020-26976
Creator: NVD / NIST
Published: 2021-01-07T14:15:12.173+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.57%

Last modified Jun 17, 2026

CVE-2020-26976 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. When a HTTPS pages was embedded in a HTTP page, and there was a service worker registered for the former, the service worker could have intercepted the request for the secure page despite the iframe not being a secure context due to the (insecure) framing. This vulnerability affects Firefox < 84.. EPSS estimates a 1.57% chance of exploitation in the next 30 days.

Description

When a HTTPS pages was embedded in a HTTP page, and there was a service worker registered for the former, the service worker could have intercepted the request for the secure page despite the iframe not being a secure context due to the (insecure) framing. This vulnerability affects Firefox < 84.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.57%

72.2th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 84.0
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1674343Issue Tracking, Permissions Required, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2021/02/msg00001.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/02/msg00002.htmlMailing List, Third Party Advisory
https://security.gentoo.org/glsa/202102-02Third Party Advisory
https://www.debian.org/security/2021/dsa-4840Third Party Advisory
https://www.debian.org/security/2021/dsa-4842Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-54/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1674343Issue Tracking, Permissions Required, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2021/02/msg00001.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/02/msg00002.htmlMailing List, Third Party Advisory
https://security.gentoo.org/glsa/202102-02Third Party Advisory
https://www.debian.org/security/2021/dsa-4840Third Party Advisory
https://www.debian.org/security/2021/dsa-4842Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-54/Vendor Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2020-26976?

How severe is CVE-2020-26976?

CVE-2020-26976 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.57% probability of exploitation in the next 30 days.

How do I fix CVE-2020-26976?

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-2020-26976?

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

Scan your code now

Source: NVD / NIST