How severe is CVE-2026-8948?

CVE-2026-8948 has a CVSS 3.x base score of 9.1, 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 none.

Is CVE-2026-8948 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-8948?

CVE-2026-8948 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-2026-8948?

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.

Does CVE-2026-8948 have an EU (EUVD) identifier?

Yes. CVE-2026-8948 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30900.

When was CVE-2026-8948 published?

CVE-2026-8948 was published on 2026-05-19 and last updated on 2026-07-15.

CVE-2026-8948

CVE-2026-8948 is a critical-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 9.1. 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-942.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 0% (35th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30900
Weakness: CWE-942
Affected product: Mozilla Firefox
Published: 2026-05-19
Last modified: 2026-07-15

Description

Same-origin policy bypass in the DOM: Networking component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

Frequently asked questions

What is CVE-2026-8948?: Same-origin policy bypass in the DOM: Networking component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.
How severe is CVE-2026-8948?: CVE-2026-8948 has a CVSS 3.x base score of 9.1, 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 none.
Is CVE-2026-8948 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-8948?: CVE-2026-8948 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-2026-8948?: 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.
Does CVE-2026-8948 have an EU (EUVD) identifier?: Yes. CVE-2026-8948 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30900.
When was CVE-2026-8948 published?: CVE-2026-8948 was published on 2026-05-19 and last updated on 2026-07-15.

References

Affected products (2)

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

More vulnerabilities in Mozilla Firefox

CVE-2026-75874 — Critical (CVSS 10.0): Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154 and Thunderbird 154.
CVE-2026-16367 — Critical (CVSS 10.0): Sandbox escape due to invalid pointer in the Disability Access APIs component. This vulnerability was fixed in Firefox…
CVE-2026-4725 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149…
CVE-2026-4692 — Critical (CVSS 10.0): Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR…
CVE-2026-4689 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was…
CVE-2026-4688 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox…

All CVEs affecting Mozilla Firefox →

Other CWE-942 vulnerabilities

CVE-2022-26969 — Critical (CVSS 9.8): In Directus before 9.7.0, the default settings of CORS_ORIGIN and CORS_ENABLED are true.
CVE-2022-31736 — Critical (CVSS 9.8): A malicious website could have learned the size of a cross-origin resource that supported Range requests. This…
CVE-2026-34449 — Critical (CVSS 9.6): SiYuan is a personal knowledge management system. Prior to version 3.6.2, a malicious website can achieve Remote Code…
CVE-2026-30924 — Critical (CVSS 9.6): qui is a web interface for managing qBittorrent instances. Versions 1.14.1 and below use a permissive CORS policy that…
CVE-2026-9739 — Critical (CVSS 9.4): Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790). During the beta phase, we implemented…
CVE-2026-61736 — Critical (CVSS 9.3): LightRAG provides simple and fast retrieval-augmented generation. Prior to 1.5.4, the server defaults to CORS_ORIGINS=*…

Browse all CWE-942 vulnerabilities →