How severe is CVE-2020-26963?

CVE-2020-26963 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2020-26963 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-26963?

CVE-2020-26963 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-26963?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2020-26963 published?

CVE-2020-26963 was published on 2020-12-09 and last updated on 2026-06-17.

CVE-2020-26963

CVE-2020-26963 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
CVSS v2: 4.3
EPSS exploit prediction: 1% (53rd percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Mozilla Firefox
Published: 2020-12-09
Last modified: 2026-06-17

Description

Repeated calls to the history and location interfaces could have been used to hang the browser. This was addressed by introducing rate-limiting to these API calls. This vulnerability affects Firefox < 83.

Frequently asked questions

What is CVE-2020-26963?: Repeated calls to the history and location interfaces could have been used to hang the browser. This was addressed by introducing rate-limiting to these API calls. This vulnerability affects Firefox < 83.
How severe is CVE-2020-26963?: CVE-2020-26963 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2020-26963 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-26963?: CVE-2020-26963 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-26963?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2020-26963 published?: CVE-2020-26963 was published on 2020-12-09 and last updated on 2026-06-17.

References

Affected products (1)

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

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