CVE-2020-35111

Name: CVE-2020-35111
Creator: NVD / NIST
Published: 2021-01-07T14:15:12.453+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 1.18%

Last modified Jun 17, 2026

CVE-2020-35111 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. When an extension with the proxy permission registered to receive <all_urls>, the proxy.onRequest callback was not triggered for view-source URLs. While web content cannot navigate to such URLs, a user opening View Source could have inadvertently leaked their IP address. EPSS estimates a 1.18% chance of exploitation in the next 30 days.

Description

When an extension with the proxy permission registered to receive <all_urls>, the proxy.onRequest callback was not triggered for view-source URLs. While web content cannot navigate to such URLs, a user opening View Source could have inadvertently leaked their IP address. This vulnerability affects Firefox < 84, Thunderbird < 78.6, and Firefox ESR < 78.6.

Metrics

CVSS 3.1

4.3/10

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

EPSS Probability

1.18%

63.8th percentile

Probability of exploitation in the next 30 days. Learn more

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=1657916Permissions 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=1657916Permissions 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-2020-35111?

How severe is CVE-2020-35111?

CVE-2020-35111 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 1.18% probability of exploitation in the next 30 days.

How do I fix CVE-2020-35111?

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-2020-35111?

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

Scan your code now

Source: NVD / NIST