How severe is CVE-2026-74978?

CVE-2026-74978 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-2026-74978 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-74978?

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-2026-74978 published?

CVE-2026-74978 was published on 2026-08-18.

CVE-2026-74978

CVE-2026-74978 is a high-severity vulnerability 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-1021.

Key facts

Severity: High (CVSS 3.x base score 8.1)
EPSS exploit prediction: 0% (16th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1021
Published: 2026-08-18
Last modified: 2026-08-18

Description

Clickjacking issue in the Widget component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.

Frequently asked questions

What is CVE-2026-74978?: Clickjacking issue in the Widget component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
How severe is CVE-2026-74978?: CVE-2026-74978 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-2026-74978 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-74978?: 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-2026-74978 published?: CVE-2026-74978 was published on 2026-08-18.

References

Other CWE-1021 vulnerabilities

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CVE-2021-23274 — Critical (CVSS 9.8): The Config UI component of TIBCO Software Inc.'s TIBCO API Exchange Gateway and TIBCO API Exchange Gateway Distribution…
CVE-2016-2496 — Critical (CVSS 9.8): The Framework UI permission-dialog implementation in Android 6.x before 2016-06-01 allows attackers to conduct…
CVE-2021-21132 — Critical (CVSS 9.6): Inappropriate implementation in DevTools in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to…
CVE-2021-21111 — Critical (CVSS 9.6): Insufficient policy enforcement in WebUI in Google Chrome prior to 87.0.4280.141 allowed an attacker who convinced a…
CVE-2024-10004 — Critical (CVSS 9.1): Opening an external link to an HTTP website when Firefox iOS was previously closed and had an HTTPS tab open could in…

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