How severe is CVE-2026-4718?

CVE-2026-4718 has a CVSS 3.x base score of 8.1, 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 none.

Is CVE-2026-4718 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-4718?

CVE-2026-4718 primarily affects Mozilla Firefox. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-4718?

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.

Does CVE-2026-4718 have an EU (EUVD) identifier?

Yes. CVE-2026-4718 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-14851.

When was CVE-2026-4718 published?

CVE-2026-4718 was published on 2026-03-24 and last updated on 2026-06-17.

CVE-2026-4718

CVE-2026-4718 is a high-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 8.1. 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-758.

Key facts

Severity: High (CVSS 3.x base score 8.1)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-14851
Weakness: CWE-758
Affected product: Mozilla Firefox
Published: 2026-03-24
Last modified: 2026-06-17

Description

Undefined behavior in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Frequently asked questions

What is CVE-2026-4718?: Undefined behavior in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
How severe is CVE-2026-4718?: CVE-2026-4718 has a CVSS 3.x base score of 8.1, 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 none.
Is CVE-2026-4718 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-4718?: CVE-2026-4718 primarily affects Mozilla Firefox. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-4718?: 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.
Does CVE-2026-4718 have an EU (EUVD) identifier?: Yes. CVE-2026-4718 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-14851.
When was CVE-2026-4718 published?: CVE-2026-4718 was published on 2026-03-24 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

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Other CWE-758 vulnerabilities

CVE-2026-4705 — Critical (CVSS 9.8): Undefined behavior in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9,…
CVE-2026-4724 — Critical (CVSS 9.1): Undefined behavior in the Audio/Video component. This vulnerability was fixed in Firefox 149 and Thunderbird 149.
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