CVE-2026-8958

Description

Information disclosure, sandbox escape in the Security: Process Sandboxing 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: high
CVSS score: 8.6 / 10
CVSS vector: AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Effective score: 8.6 / 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-2026-8958.json
Linked Threat: CVE-2026-8958 — CVE-2026-8958

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 14:16:52 UTC
NVD last modified: 2026-05-20 15:01:41 UTC
NVD CVSS v3.1: 8.6 / 10 HIGH source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Exploitability subscore: 3.9 / 10
Impact subscore: 4.0 / 10
EPSS score: 0.0004 (probability of exploitation in next 30 days)
EPSS percentile: 13.59% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

NVD-assigned CWE(s): CWE-668, CWE-693 (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-2026-30907
Assigner: mozilla
Published: May 19, 2026, 12:29:54 PM
Updated: May 19, 2026, 5:10:50 PM
EUVD base score (CVSS 3.1): 8.6 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
EUVD-reported EPSS: 0.0600
Aliases: GHSA-gm4c-ph85-6chj

ENISA description: Information disclosure, sandbox escape in the Security: Process Sandboxing 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 (15)

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
http://www.mozilla.org/security/announce/2026/mfsa2026-46.html rapid7:www.mozilla.org
https://attackerkb.com/topics/CVE-2026-8958 rapid7:attackerkb.com
http://cwe.mitre.org/data/definitions/668.html rapid7:cwe.mitre.org
http://cwe.mitre.org/data/definitions/693.html rapid7:cwe.mitre.org
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-30907 rapid7:euvd.enisa.europa.eu
https://www.mozilla.org/security/advisories/mfsa2026-51/ tenable:www.mozilla.org
https://nvd.nist.gov/vuln/detail/CVE-2026-8958 tenable:nvd.nist.gov
https://www.cve.org/CVERecord?id=CVE-2026-8958 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/mfsa2026-48/ tenable:www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-50/ tenable:www.mozilla.org
https://bugzilla.mozilla.org/show_bug.cgi?id=2034713 tenable:bugzilla.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=2034713 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 (13)

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

CVE-2026-8958 - Vulnerability Details - OpenCVE

web:app.opencve.io

Remediation No vendor fix or workaround currently provided. OpenCVE Recommended Actions Upgrade Firefox to version 151 or the ESR 140.11 release or later to obtain the sandbox fix . Upgrade Thunderbird to version 151 or the ESR 140.11 release or later to obtain the sandbox fix .

2026-05-23 22:18 UTC
CVE-2026-8958 - Information disclosure, sandbox escape in the Security ...

web:cvefeed.io

The following products are affected by CVE-2026-8958 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.

2026-05-23 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
CVE-2026-8958 - Exploits & Severity - Feedly

web:feedly.com

A vulnerability classified as critical has been found in Mozilla Firefox up to 150 . The impacted element is an unknown function of the component Process Sandboxing . This manipulation causes sandbox issue. This vulnerability is tracked as CVE-2026-8958 . The attack is possible to be carried out remotely. No exploit exists. It is recommended to upgrade the affected component.

2026-05-23 22:18 UTC
CVE-2026-8958 - GitHub Advisory Database

web:github.com

GitHub is where people build software. More than 150 million people use GitHub to discover, fork, and contribute to over 420 million projects.

2026-05-23 22:18 UTC
CVE-2026-8958 | Security Details | Sonatype Guide

web:guide.sonatype.com

Technical security analysis for CVE-2026-8958 . CVSS 8.6 severity. View CVSS vectors, CWE classifications, and exploit maturity ratings.

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-2026-8958 - security-tracker.debian.org

web:security-tracker.debian.org

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

2026-05-23 22:18 UTC
CVE-2026-8958 - vulmon.com

web:vulmon.com

Vulnerability details of CVE-2026-8958 CVE-2026-8958 - Information Disclosure and Sandbox Escape in Firefox Process Sandboxing Component

2026-05-23 22:18 UTC
CVE-2026-8958 - High Vulnerability - TheHackerWire

web:www.thehackerwire.com

CVE-2026-8958 is a High severity vulnerability (CVSS 8.6). Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11,...

2026-05-23 22:18 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
Emergency patch issued for Microsoft Office, 365 over hacking threat - MSN

web:www.msn.com

Microsoft suggests the threat is being used in phishing attacks against vulnerable systems since successful exploitation requires local access to the PC.

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

web:www.rapid7.com

vulnerability MFSA2026-46 Firefox: Security Vulnerabilities fixed in Firefox 151 ( CVE-2026-8958 )

2026-05-26 02:58 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-8958.json.

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