CVE-2026-8956

Description

Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Overview

State: PUBLISHED
Assigner (CNA): mozilla
CVSS severity: critical
CVSS score: 9.8 / 10
CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Effective score: 9.8 / 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-2026-8956.json
Linked Threat: CVE-2026-8956 — CVE-2026-8956

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 14:31:07 UTC
NVD CVSS v3.1: 9.8 / 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:H
Exploitability subscore: 3.9 / 10
Impact subscore: 5.9 / 10
EPSS score: 0.0005 (probability of exploitation in next 30 days)
EPSS percentile: 15.17% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

NVD-assigned CWE(s): CWE-190 (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-2026-30904
Assigner: mozilla
Published: May 19, 2026, 12:29:51 PM
Updated: May 19, 2026, 5:10:49 PM
EUVD base score (CVSS 3.1): 9.8 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EUVD-reported EPSS: 0.0600
Aliases: GHSA-22h3-6xv6-p2px

ENISA description: Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

EUVD references (5)

Affected products (2)

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

Affected products — CPE 2.3 (4) 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:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

Vendor references (5)

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

Web references (14)

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/mfsa2026-48.html rapid7:www.mozilla.org
https://attackerkb.com/topics/CVE-2026-8956 rapid7:attackerkb.com
http://www.mozilla.org/security/announce/2026/mfsa2026-46.html rapid7:www.mozilla.org
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-30904 rapid7:euvd.enisa.europa.eu
http://cwe.mitre.org/data/definitions/190.html rapid7:cwe.mitre.org
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=2032427 tenable:bugzilla.mozilla.org
https://nvd.nist.gov/vuln/detail/CVE-2026-8956 tenable:nvd.nist.gov
https://www.cve.org/CVERecord?id=CVE-2026-8956 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

NVD-tagged references (5)

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=2032427 security@mozilla.org Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-46/ security@mozilla.org Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-48/ 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 (16)

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

CVE-2026-8956 - Vulnerability Details - OpenCVE

web:app.opencve.io

Remediation No vendor fix or workaround currently provided. OpenCVE Recommended Actions Install Firefox 151 or newer, or ESR 140.11 or later. Install Thunderbird 151 or newer, or ESR 140.11 or later. Remove or uninstall older Firefox binaries to prevent accidental use of the vulnerable component.

2026-05-23 22:18 UTC
Oracle Critical Patch Update (CPU) April 2026 for Oracle Java SE

web:docs.oracle.com

Oracle Critical Patch Update (CPU) April 2026 for Oracle Java SE Services: Java Management Release Date: April 21, 2026

2026-05-23 22:18 UTC
CVE-2026-8956 | Security Details | Sonatype Guide

web:guide.sonatype.com

Technical security analysis for CVE-2026-8956 . CVSS 9.8 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
Security Update Guide - Microsoft

web:msrc.microsoft.com

The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.

2026-05-23 22:18 UTC
Nvd - Cve-2026-8956

web:nvd.nist.gov

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

2026-05-23 22:18 UTC
Landing Page | ServiceNow Common Vulnerabilities & Exposures (CVE ...

web:support.servicenow.com

Overview The advisories below document publicly disclosed Common Vulnerabilities and Exposures ( CVEs ) in the Now Platform by ServiceNow. Because ServiceNow uses various methods to communicate vulnerability information, patches, and other fixes, customers should review family, security patch , and hotfix release notes, which are available at https://docs.servicenow.com, for a complete list of ...

2026-05-23 22:18 UTC
CVE-2026-8956 - Critical Vulnerability - TheHackerWire

web:www.thehackerwire.com

CVE-2026-8956 is a Critical severity vulnerability (CVSS 9.8). Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and...

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
Patch Tuesday May 2026: Security Updates & CVE Analysis

web:zecurit.com

Get the complete breakdown of Microsoft's May 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .

2026-05-23 22:18 UTC
Firefox & Thunderbird CVE-2026-8956: System Control Vulnerability

web:cve.halosecurity.com

Learn about CVE-2026-8956 impacting Firefox and Thunderbird. An integer overflow in the JAR component could allow external attackers to gain system control through memory corrup...

2026-05-26 02:58 UTC
CVE-2026-8956 - Integer overflow in the Networking: JAR component

web:cvefeed.io

The following products are affected by CVE-2026-8956 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

2026-05-26 02:58 UTC
CVE-2026-8956 - Exploits & Severity - Feedly

web:feedly.com

Mitigation Update Firefox to version 151 or later, or Firefox ESR to version 140.11 or later. Users unable to patch immediately should consider disabling JAR file handling if possible, or limiting network exposure to untrusted sources.

2026-05-26 02:58 UTC
CVE-2026-8956: Integer overflow in the Networking: JAR component. This ...

web:research.averlon.ai

CVE-2026-8956 : Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

2026-05-26 02:58 UTC
SecuriTricks - CVE-2026-8956 - 9.8/10

web:securitricks.com

CVE CVE-2026-8956 - Score : 9.8 - Source : security@mozilla.org - Description : Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

2026-05-26 02:58 UTC
Critical Patches Issued for Microsoft Products, May 12, 2026

web:www.cisecurity.org

<p>Multiple vulnerabilities have been discovered in Microsoft products, the most severe of which could allow for remote code execution. Successful exploitation of the most severe of these vulnerabilities could result in an attacker gaining the same privileges as the logged-on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or ...

2026-05-26 02:58 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-8956.json.

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