What is CVE-2020-6811?

CVE-2020-6811 is a high-severity vulnerability in Mozilla Firefox, classified under Command Injection. CVSS score: 8.8/10. Published 2020-03-25.

How severe is CVE-2020-6811?

High severity. CVSS v3 base score is 8.8 out of 10.

Is CVE-2020-6811 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

RCE in Mozilla Firefox

CVE-2020-6811

The 'Copy as cURL' feature of Devtools' network tab did not properly escape the HTTP method of a request, which can be controlled by the website. If a user used the 'Copy as Curl' feature and pasted the command into a terminal, it could have resulted in command injection and arbitrary command execution. This vulnerability affects Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

Vulnerability class: Command Injection (OS Command Injection)

Published 2020-03-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.033 (88.0th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 88.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.033 · newest: 0.033 · change: 0.000

Affected products

Mozilla Firefox — versions unspecified
Mozilla Firefox Esr — versions unspecified
Mozilla Firefox Esr
Mozilla Thunderbird — versions unspecified
Canonical Ubuntu Linux — versions 16.04, 18.04, 19.10

Weakness classification (CWE)

CWE-77 — Command Injection

Public proof-of-concept exploits

ARPSyndicate/cve-scores

References

www.mozilla.org/security/advisories/mfsa2020-08/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2020-10/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2020-09/ (Vendor Advisory)
bugzilla.mozilla.org/show_bug.cgi (Exploit, Issue Tracking, Vendor Advisory)
usn.ubuntu.com/4328-1/ (vendor-advisory, Third Party Advisory)
usn.ubuntu.com/4335-1/ (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2020-6811?: CVE-2020-6811 is a high-severity vulnerability in Mozilla Firefox, classified under Command Injection. CVSS score: 8.8/10. Published 2020-03-25.
How severe is CVE-2020-6811?: High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2020-6811 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.