How severe is CVE-2020-12389?

CVE-2020-12389 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-12389 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-12389?

CVE-2020-12389 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-12389?

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

When was CVE-2020-12389 published?

CVE-2020-12389 was published on 2020-05-26 and last updated on 2026-06-17.

CVE-2020-12389

CVE-2020-12389 is a critical-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 10.0. 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-20.

Key facts

Severity: Critical (CVSS 3.x base score 10.0)
CVSS v2: 7.5
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Mozilla Firefox
Published: 2020-05-26
Last modified: 2026-06-17

Description

The Firefox content processes did not sufficiently lockdown access control which could result in a sandbox escape. *Note: this issue only affects Firefox on Windows operating systems.*. This vulnerability affects Firefox ESR < 68.8 and Firefox < 76.

Frequently asked questions

What is CVE-2020-12389?: The Firefox content processes did not sufficiently lockdown access control which could result in a sandbox escape. *Note: this issue only affects Firefox on Windows operating systems.*. This vulnerability affects Firefox ESR < 68.8 and Firefox < 76.
How severe is CVE-2020-12389?: CVE-2020-12389 has a CVSS 3.x base score of 10.0, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-12389 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-12389?: CVE-2020-12389 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-12389?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-12389 published?: CVE-2020-12389 was published on 2020-05-26 and last updated on 2026-06-17.

References

Affected products (2)

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

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