Security readout for executives and security teams
Plain-English summary
CVE-2026-4711 is a critical memory-safety flaw in Mozilla’s Widget: Cocoa component. Mozilla says it is fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. Organizations should prioritize updating Mozilla desktop clients, especially on macOS environments where Cocoa is relevant.
Executive priority
Treat as urgent patching for Mozilla desktop software. The vulnerability is rated critical and could affect confidentiality, integrity, and availability. No active exploitation is confirmed in the supplied sources, but the low-complexity CVSS profile warrants rapid remediation.
Technical view
The issue is a use-after-free vulnerability, CWE-416, in Widget: Cocoa. The CVSS 3.1 score is 9.8 with network attack vector, low complexity, no privileges, and high confidentiality, integrity, and availability impact. Public sources do not provide exploit details in the supplied bundle.
Likely exposure
Likely exposure is endpoints running Firefox, Firefox ESR, or Thunderbird before the Mozilla fixed releases named for this CVE. The source bundle does not enumerate every vulnerable prior version, so validation should compare installed versions against Mozilla advisories.
Exploitation context
CISA KEV status is false in the supplied data, and no cited source states active exploitation. The CVSS vector indicates potentially remote, low-complexity exploitation without privileges or user interaction, but public evidence in the bundle does not describe a working exploit.
Researcher notes
The bundle identifies the flaw class and component but does not include root-cause detail, proof-of-concept status, or vulnerable version ranges beyond fixed releases. Avoid assuming exploitation or macOS-only exposure without further advisory detail, although Cocoa strongly suggests Apple platform relevance.
Mitigation direction
- Update Firefox to version 149 or later where applicable.
- Update Firefox ESR to version 140.9 or later.
- Update Thunderbird to version 149 or later where applicable.
- Update Thunderbird ESR to version 140.9 or later.
- Review Mozilla advisories for product-specific update guidance.
Validation and detection
- Inventory installed Firefox, Firefox ESR, and Thunderbird versions.
- Confirm versions meet or exceed Mozilla’s fixed releases.
- Check endpoint management reports for failed or deferred browser updates.
- Review Mozilla advisories for any platform-specific applicability notes.
- Track CVE-2026-4711 for changes in exploitation status.
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-416: 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-2026-4711 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
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2017002CVE 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 After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.