Security readout for executives and security teams
Plain-English summary
CVE-2026-4719 is a high-severity Mozilla flaw in text graphics handling. Mozilla says it is fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The published impact is denial of service, not data theft or code execution. Organizations should prioritize updating managed browsers and mail clients.
Executive priority
Treat as a prompt endpoint update item. The known impact is service disruption rather than compromise, but browsers and mail clients are broad enterprise attack surfaces. Prioritize patching exposed user fleets and managed images during the next urgent maintenance cycle.
Technical view
The issue is described as incorrect boundary conditions in the Graphics: Text component, mapped to CWE-119. CVSS 3.1 is 7.5: network-accessible, low complexity, no privileges, no user interaction, with high availability impact only. Public details do not describe root cause, crash conditions, or exploit mechanics.
Likely exposure
Exposure is likely wherever Mozilla Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR are below the fixed releases named by Mozilla. Workstations, VDI images, kiosk systems, and email clients are the primary inventory targets. The source bundle does not provide a broader affected-version range.
Exploitation context
CISA KEV status is false in the provided data, and the cited sources do not state active exploitation. The CVSS vector indicates remote network attack potential without privileges or user interaction, but public sources do not provide exploit details or proof-of-concept status.
Researcher notes
The public description is sparse. Bugzilla and Mozilla advisories are the authoritative references, but the bundle only confirms component, CWE, CVSS, and fixed releases. Avoid assuming code execution or exploit availability without additional vendor or KEV evidence.
Mitigation direction
- Update Firefox to version 149 or later.
- Update Firefox ESR to version 140.9 or later.
- Update Thunderbird to version 149 or later.
- Update Thunderbird ESR to version 140.9 or later.
- Check Mozilla advisories for platform-specific deployment guidance.
Validation and detection
- Inventory installed Firefox and Thunderbird versions across endpoints.
- Confirm ESR channels are at 140.9 or later.
- Confirm rapid-release channels are at 149 or later.
- Review vulnerability scanner results against CVE-2026-4719.
- Monitor Mozilla advisories for revised affected-version details.
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-119: 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-2026-4719 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
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2016367CVE 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.
Improper Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.