How severe is CVE-2020-12393?

CVE-2020-12393 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-12393 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-12393?

CVE-2020-12393 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-12393?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-12393 published?

CVE-2020-12393 was published on 2020-05-26 and last updated on 2026-06-17.

CVE-2020-12393

CVE-2020-12393 is a high-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-78.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 4.6
EPSS exploit prediction: 1% (59th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
Affected product: Mozilla Firefox
Published: 2020-05-26
Last modified: 2026-06-17

Description

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. *Note: this issue only affects Firefox on Windows operating systems.*. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.

Frequently asked questions

What is CVE-2020-12393?: 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. *Note: this issue only affects Firefox on Windows operating systems.*. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.
How severe is CVE-2020-12393?: CVE-2020-12393 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-12393 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-12393?: CVE-2020-12393 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-12393?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-12393 published?: CVE-2020-12393 was published on 2020-05-26 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

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