CVE-2026-8948

Description

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

Overview

State: PUBLISHED
Assigner (CNA): mozilla
CVSS severity: critical
CVSS score: 9.1 / 10
CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Effective score: 9.1 / 10 CRITICAL source: CNA overview
CWE(s): —
Reserved: 2026-05-19
Published: 2026-05-19 12:29 UTC
Last updated: 2026-05-19 17:10 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/8xxx/CVE-2026-8948.json
Linked Threat: CVE-2026-8948 — CVE-2026-8948

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-05-19 14:16:51 UTC
NVD last modified: 2026-05-20 14:53:13 UTC
NVD CVSS v3.1: 9.1 / 10 CRITICAL source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploitability subscore: 3.9 / 10
Impact subscore: 5.2 / 10
EPSS score: 0.0003 (probability of exploitation in next 30 days)
EPSS percentile: 8.93% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

NVD-assigned CWE(s): CWE-942 (differs from the CNA list above)

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-30900
Assigner: mozilla
Published: May 19, 2026, 12:29:39 PM
Updated: May 19, 2026, 5:10:52 PM
EUVD base score (CVSS 3.1): 9.1 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EUVD-reported EPSS: 0.0400
Aliases: GHSA-j9gx-gpjh-cwc4

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

EUVD references (3)

Affected products (2)

Vendor	Product	Versions	Platforms
Mozilla	Firefox	`151` (unaffected)	—
Mozilla	Thunderbird	`151` (unaffected)	—

Affected products — CPE 2.3 (2) NVD

NVD's normalized CPE 2.3 matchers, used by vendor tools (vulnerability scanners, asset managers) for automated detection. Compare with the CNA's free-text "Affected products" section above.

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

Vendor references (3)

References embedded in the original CVE record by the assigning CNA.

Web references (11)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

http://www.mozilla.org/security/announce/2026/mfsa2026-50.html rapid7:www.mozilla.org
http://www.mozilla.org/security/announce/2026/mfsa2026-46.html rapid7:www.mozilla.org
https://attackerkb.com/topics/CVE-2026-8948 rapid7:attackerkb.com
http://cwe.mitre.org/data/definitions/942.html rapid7:cwe.mitre.org
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-30900 rapid7:euvd.enisa.europa.eu
https://www.mozilla.org/security/advisories/mfsa2026-50/ tenable:www.mozilla.org
https://nvd.nist.gov/vuln/detail/CVE-2026-8948 tenable:nvd.nist.gov
https://www.cve.org/CVERecord?id=CVE-2026-8948 tenable:www.cve.org
https://www.first.org/epss/ tenable:www.first.org
https://www.mozilla.org/security/advisories/mfsa2026-46/ tenable:www.mozilla.org
https://bugzilla.mozilla.org/show_bug.cgi?id=2038803 tenable:bugzilla.mozilla.org

NVD-tagged references (3)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://bugzilla.mozilla.org/show_bug.cgi?id=2038803 security@mozilla.org Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-46/ security@mozilla.org Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-50/ security@mozilla.org Vendor Advisory

Remediations (16)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

CVE-2026-8948 - Vulnerability Details - OpenCVE

web:app.opencve.io

Remediation No vendor fix or workaround currently provided. OpenCVE Recommended Actions Upgrade all Firefox installations to version 151 or later Upgrade all Thunderbird installations to version 151 or later Remove or disable any older Firefox versions from the environment to prevent inadvertent use

2026-05-23 22:18 UTC
CVE-2026-8948 - Exploits & Severity - Feedly

web:feedly.com

This issue affects some unknown processing of the component Networking Component . Performing a manipulation results in permissive cross-domain policy with untrusted domains. This vulnerability is known as CVE-2026-8948 . Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is advised.

2026-05-23 22:18 UTC
CVE-2026-8948 | Security Details | Sonatype Guide

web:guide.sonatype.com

Technical security analysis for CVE-2026-8948 . CVSS 9.1 severity. View CVSS vectors, CWE classifications, and exploit maturity ratings.

2026-05-23 22:18 UTC
Patch Tuesday, May 2026 Edition - Krebs on Security

web:krebsonsecurity.com

Microsoft expects that exploitation is more likely. May's Patch Tuesday is a welcome respite from April, which saw Microsoft fix a near-record 167 security flaws.

2026-05-23 22:18 UTC
Nvd - Cve-2026-8948

web:nvd.nist.gov

An official website of the United States government Here's how you know

2026-05-23 22:18 UTC
Security Update Guide - Microsoft

web:portal.msrc.microsoft.com

The Security Update Guide provides information on the latest Microsoft security updates, helping users understand and address potential vulnerabilities effectively.

2026-05-23 22:18 UTC
CVE-2026-8948 : Same-Origin Policy Bypass in Firefox Networking Component

web:securityvulnerability.io

Discover the same-origin policy bypass vulnerability affecting Firefox's networking component. Learn more about CVE-2026-8948 now.

2026-05-23 22:18 UTC
April 2026 Patch Tuesday: Updates and Analysis | CrowdStrike

web:www.crowdstrike.com

Microsoft's April 2026 Patch Tuesday addresses 164 CVEs , featuring 8 Critical vulnerabilities, one exploited zero-day, and one disclosed zero-day.

2026-05-23 22:18 UTC
Oracle Critical Patch Update Advisory - April 2026

web:www.oracle.com

This Critical Patch Update contains 481 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at April 2026 Critical Patch Update: Executive Summary and Analysis.

2026-05-23 22:18 UTC
CVE-2026-8948 - Critical Vulnerability - TheHackerWire

web:www.thehackerwire.com

CVE-2026-8948 is a Critical severity vulnerability (CVSS 9.1). Same-origin policy bypass in the DOM: Networking component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

2026-05-23 22:18 UTC
CISA Warns of Exploited Microsoft Defender 0-Day Flaws

web:cyberpress.org

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added two actively exploited Microsoft Defender vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog, issuing an urgent remediation directive for federal agencies with a due date of June 3, 2026 .

2026-05-26 02:58 UTC
CVE-2026-8948: Same-origin policy bypass in the DOM: Networking ...

web:research.averlon.ai

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

2026-05-26 02:58 UTC
February's Patch Tuesday release fixes 59 flaws ... - Computerworld

web:www.computerworld.com

Each month, the team at Readiness analyzes the latest Patch Tuesday updates from Microsoft and provides detailed, actionable testing guidance. The company's Patch Tuesday release for February ...

2026-05-26 02:58 UTC
Microsoft Technical Security Notifications

web:www.microsoft.com

Security Update Guide Notifications Microsoft's free Security Update Guide Notifications provide links to security-related software updates and notification of re-released security updates. These notifications are sent via email throughout the month as needed.

2026-05-26 02:58 UTC
Emergency patch issued for Microsoft Office, 365 over hacking threat - MSN

web:www.msn.com

Original story: Microsoft has released an emergency patch for a vulnerability in the company's Office programs that's already being exploited by hackers.

2026-05-26 02:58 UTC
Rapid7 Vulnerability Database

web:www.rapid7.com

Rapid7's VulnDB is curated repository of vetted computer software exploits and exploitable vulnerabilities.

2026-05-26 02:58 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-8948.json.

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              "integrityImpact": "HIGH",
              "privilegesRequired": "NONE",
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