CVE-2026-8948

CRITICAL

Published May 19, 2026 Modified May 20, 2026 CWE-942

Description

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

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CVSS v3.1 Score

9.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0039

Probability of exploitation

0.31%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-942 CWE-942

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 151.0.0
mozilla	thunderbird	< 151.0.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2026-46/ https://www.mozilla.org/security/advisories/mfsa2026-50/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=2038803

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. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-8948? +

CVE-2026-8948 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0039, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-8948? +

CVE-2026-8948 affects products from mozilla, specifically: firefox, thunderbird. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-8948? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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