CVE-2026-8946

CVEs › CVE-2026-8946

Description

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Overview

State: PUBLISHED
Assigner (CNA): mozilla
CVSS severity: high
CVSS score: 7.5 / 10
CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Effective score: 7.5 / 10 HIGH 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-2026-8946.json
Linked Threat: CVE-2026-8946 — CVE-2026-8946

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 14:16:50 UTC
NVD last modified: 2026-05-19 18:50:01 UTC
NVD CVSS v3.1: 7.5 / 10 HIGH 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:N/A:N
Exploitability subscore: 3.9 / 10
Impact subscore: 3.6 / 10
EPSS score: 0.0004 (probability of exploitation in next 30 days)
EPSS percentile: 11.34% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

NVD-assigned CWE(s): CWE-119 (differs from the CNA list above)

NVD / KEV / EPSS data refreshed 2026-05-25 00:33 UTC. Re-run the 🛰 Backfill from NVD button above to refresh.

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-2026-30894
Assigner: mozilla
Published: May 19, 2026, 12:29:36 PM
Updated: May 19, 2026, 5:10:45 PM
EUVD base score (CVSS 3.1): 7.5 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EUVD-reported EPSS: 0.0500
Aliases: GHSA-q9p7-4943-m5gr

ENISA description: Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

EUVD references (6)

Affected products (2)

Vendor	Product	Versions	Platforms
Mozilla	Firefox	`115.36` (unaffected), `140.11` (unaffected), `151` (unaffected)	—
Mozilla	Thunderbird	`140.11` (unaffected), `151` (unaffected)	—

Affected products — CPE 2.3 (3) 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:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

Vendor references (6)

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

Web references (16)

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/mfsa2026-51.html rapid7:www.mozilla.org
http://www.mozilla.org/security/announce/2026/mfsa2026-47.html rapid7:www.mozilla.org
http://www.mozilla.org/security/announce/2026/mfsa2026-48.html rapid7:www.mozilla.org
http://cwe.mitre.org/data/definitions/119.html rapid7:cwe.mitre.org
http://www.mozilla.org/security/announce/2026/mfsa2026-46.html rapid7:www.mozilla.org
https://attackerkb.com/topics/CVE-2026-8946 rapid7:attackerkb.com
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-30894 rapid7:euvd.enisa.europa.eu
https://www.mozilla.org/security/advisories/mfsa2026-48/ tenable:www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-50/ tenable:www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-51/ tenable:www.mozilla.org
https://bugzilla.mozilla.org/show_bug.cgi?id=2029070 tenable:bugzilla.mozilla.org
https://nvd.nist.gov/vuln/detail/CVE-2026-8946 tenable:nvd.nist.gov
https://www.cve.org/CVERecord?id=CVE-2026-8946 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://www.mozilla.org/security/advisories/mfsa2026-47/ tenable:www.mozilla.org

NVD-tagged references (6)

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=2029070 security@mozilla.org Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-46/ security@mozilla.org Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-47/ security@mozilla.org Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-48/ security@mozilla.org Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-50/ security@mozilla.org Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-51/ security@mozilla.org Vendor Advisory

Remediations (18)

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

CVE-2026-8946 - Vulnerability Details - OpenCVE

web:app.opencve.io

Remediation No vendor fix or workaround currently provided. OpenCVE Recommended Actions Upgrade Mozilla Firefox to version 151 or newer, or to Firefox ESR 115.36 or ESR 140.11, and upgrade Thunderbird to version 151 or ESR 140.11 to receive the official fix .

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 .

2026-05-23 22:18 UTC
Microsoft Patch Tuesday April 2026 - 168 Vulnerabilities Fixed ...

web:cybersecuritynews.com

Microsoft has released its April 2026 Patch Tuesday security update, addressing 168 vulnerabilities across its product portfolio including one actively exploited zero-day and one publicly disclosed flaw that organizations must prioritize immediately.

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-2026-8946

web:nvd.nist.gov

Official websites use .gov A .gov website belongs to an official government organization in the United States.

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
Security Vulnerabilities fixed in Firefox 151 — Mozilla

web:www.mozilla.org

# CVE - 2026 -8969: Mitigation bypass in the DOM: Security component Reporter Atsushi Sada Impact low References Bug 2031123 # CVE - 2026 -8970: Privilege escalation in the Security component Reporter pakhunov.anton.n Impact low References Bug 2032174 # CVE - 2026 -8971: Same-origin policy bypass in the Networking: JAR component Reporter Surya Dev Singh ...

2026-05-23 22:18 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.

2026-05-23 22:18 UTC
CVE-2026-8946 - High Vulnerability - TheHackerWire

web:www.thehackerwire.com

CVE-2026-8946 is a High severity vulnerability (CVSS 7.5). Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox...

2026-05-23 22:18 UTC
Windows 11 April 2026 Update tested: What's new, improved and fixed

web:www.windowslatest.com

Windows 11 April 2026 update adds Narrator Copilot support, faster Settings, File Explorer fixes, and key security improvements.

2026-05-23 22:18 UTC
CVE-2026-8946 - Exploits & Severity - Feedly

web:feedly.com

May 19, 2026 at 7:05 AM / VulDB Recent Entries CVE Assignment NVD published the first details for CVE-2026-8946 May 19, 2026 at 7:16 AM CVSS A CVSS base score of 7.5 has been assigned.

2026-05-26 02:58 UTC
CVE-2026-8946 - security-tracker.debian.org

web:security-tracker.debian.org

Vulnerable and fixed packages The table below lists information on source packages.

2026-05-26 02:58 UTC
Addressing Exchange Server May 2026 vulnerability CVE-2026-42897

web:techcommunity.microsoft.com

We wanted to tell you how to address the Exchange Server May 2026 vulnerability CVE - 2026 -42897.

2026-05-26 02:58 UTC
CVE-2026-42897 Exchange OWA Mitigation M2: What Admins Must Verify

web:windowsforum.com

Microsoft's Fastest Fix Is a Mitigation , Not a Patch The important detail in Microsoft's May 14 notice is that there is no permanent Exchange security update available yet for CVE - 2026 -42897. Microsoft says it is working on one and will release it later for affected supported paths, but today's defensive action is mitigation .

2026-05-26 02:58 UTC
Microsoft's May 2026 Patch Tuesday Fixes 130+ Vulnerabilities ...

web:windowsreport.com

Microsoft has released its May 2026 Patch Tuesday updates for Windows 11 and Windows 10, shipping as KB5089549 and KB5087544. The updates include fixes for more than 130 security vulnerabilities across Windows, Office, SharePoint, DNS components, and core system services, as Bleeping Computer writes. While no publicly disclosed zero-day vulnerabilities were reported this month, the […]

2026-05-26 02:58 UTC
May 2026 Patch Tuesday: Updates and Analysis | CrowdStrike

web:www.crowdstrike.com

Microsoft has released security updates for 130 vulnerabilities, including 30 critical, in its May 2026 Patch Tuesday rollout.

2026-05-26 02:58 UTC
Microsoft Confirms Active 0-Day Exploit—Check Emergency Mitigation

web:www.forbes.com

Updated May 18: This article has been updated to include further details on the emergency mitigation process recommended by Microsoft after the CVE - 2026 -42897 Exchange Server zero-day was ...

2026-05-26 02:58 UTC
Security Vulnerabilities fixed in Firefox 151 - Mozilla

web:www.mozilla.org

# CVE - 2026 -8962: Mitigation bypass in the DOM: Security component Reporter Manojkumar Jaganathan Impact low

2026-05-26 02:58 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-8946.json.

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              "confidentialityImpact": "HIGH",
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