How severe is CVE-2020-15669?

CVE-2020-15669 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-15669 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-15669?

CVE-2020-15669 primarily affects Mozilla Firefox Esr. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-15669?

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-2020-15669 published?

CVE-2020-15669 was published on 2020-10-01 and last updated on 2026-06-17.

CVE-2020-15669

CVE-2020-15669 is a high-severity vulnerability in Mozilla Firefox Esr with a CVSS 3.x base score of 8.8. 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-416.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.8
EPSS exploit prediction: 1% (62nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-416
Affected product: Mozilla Firefox Esr
Published: 2020-10-01
Last modified: 2026-06-17

Description

When aborting an operation, such as a fetch, an abort signal may be deleted while alerting the objects to be notified. This results in a use-after-free and we presume that with enough effort it could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 68.12 and Thunderbird < 68.12.

Frequently asked questions

What is CVE-2020-15669?: When aborting an operation, such as a fetch, an abort signal may be deleted while alerting the objects to be notified. This results in a use-after-free and we presume that with enough effort it could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 68.12 and Thunderbird < 68.12.
How severe is CVE-2020-15669?: CVE-2020-15669 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-15669 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-15669?: CVE-2020-15669 primarily affects Mozilla Firefox Esr. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-15669?: 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-2020-15669 published?: CVE-2020-15669 was published on 2020-10-01 and last updated on 2026-06-17.

References

Affected products (2)

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

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