Security readout for executives and security teams
Plain-English summary
CVE-2026-4716 is a critical Mozilla JavaScript engine memory issue fixed in Firefox and Thunderbird updates. The published scoring indicates possible high confidentiality and availability impact. No provided source says it is being actively exploited, and it is not listed as KEV in the supplied data.
Executive priority
Prioritize enterprise rollout promptly, especially for desktop and email-client fleets. The issue is critical by CVSS and affects widely deployed software, but current supplied evidence does not show active exploitation.
Technical view
Mozilla describes incorrect boundary conditions and uninitialized memory in the JavaScript Engine component, mapped to CWE-908. It was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. CVSS 3.1 is 9.1: network, low complexity, no privileges, no user interaction, high confidentiality, no integrity, high availability impact.
Likely exposure
Organizations using Mozilla Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR before the fixed releases may be exposed. Exposure is most relevant on managed desktops, VDI images, email clients, and systems where browser or mail-client updates lag.
Exploitation context
The supplied CVSS vector indicates remote network attack potential with low complexity and no privileges or user interaction. However, the source bundle does not provide exploit details, proof-of-concept status, or active exploitation evidence. KEV status is false in the supplied data.
Researcher notes
Public detail is limited to Mozilla’s description, CVSS, CWE-908, and fixed-release advisories. Avoid assuming exploitability mechanics beyond the published vector. Bugzilla and Mozilla advisories should be monitored for additional technical detail or revised product scope.
Mitigation direction
- Update Firefox to version 149 or Firefox ESR to 140.9 where applicable.
- Update Thunderbird to version 149 or Thunderbird 140.9 where applicable.
- Use vendor-supported update channels for managed endpoint deployment.
- If updates cannot be deployed, consult Mozilla advisories for supported guidance.
- Track Mozilla advisories for revisions or additional affected-version clarification.
Validation and detection
- Inventory Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR versions across endpoints.
- Confirm installed versions meet or exceed the Mozilla fixed releases.
- Check endpoint-management and vulnerability-scanner results for CVE-2026-4716.
- Validate that golden images and VDI templates include the fixed versions.
- Review exception lists for systems unable to receive Mozilla updates.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-908: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-4716 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H3.95.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2018592CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-20/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-22/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-23/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-24/CVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Use of Uninitialized Resource
Use of Uninitialized Resource represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.