Security readout for executives and security teams
Plain-English summary
CVE-2026-4724 is a critical Mozilla issue involving undefined behavior in the Audio/Video component. Mozilla states it was fixed in Firefox 149 and Thunderbird 149. The published CVSS score is 9.1, indicating potential serious confidentiality and integrity impact. No provided source says it is being actively exploited.
Executive priority
Treat as urgent patching for environments using Firefox or Thunderbird. The impact rating is critical, but current evidence does not show confirmed exploitation. Prioritize rapid update validation over emergency incident response unless internal telemetry indicates suspicious activity.
Technical view
The CVE describes CWE-758 undefined behavior in Mozilla’s Audio/Video component. The CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Mozilla advisories list fixes in Firefox 149 and Thunderbird 149. The public bundle does not provide deeper root-cause details or exploit conditions.
Likely exposure
Organizations using Mozilla Firefox or Thunderbird builds that have not received the Mozilla fixes referenced for version 149 should treat exposure as possible. Exposure confirmation requires checking installed product versions against Mozilla’s advisories and enterprise software inventory.
Exploitation context
The scoring indicates network-reachable, low-complexity exploitation with no privileges or user interaction required. However, the provided sources do not confirm public exploit availability or active exploitation, and the CVE is not listed as KEV in the supplied data.
Researcher notes
Public details are limited to undefined behavior in the Audio/Video component, CVSS metadata, and Mozilla fixed-version advisories. Bugzilla may contain restricted or evolving details. Avoid assuming affected-version ranges beyond Mozilla guidance; validate against advisory updates and installed product versions.
Mitigation direction
- Update Firefox to Mozilla’s fixed release identified in the advisory.
- Update Thunderbird to Mozilla’s fixed release identified in the advisory.
- Check Mozilla advisories for any product-specific deployment guidance.
- Prioritize managed endpoints, VDI images, and systems using bundled Mozilla components.
Validation and detection
- Inventory installed Firefox and Thunderbird versions across endpoints.
- Confirm systems are on the Mozilla fixed versions or later.
- Review patch-management reports for failed Mozilla updates.
- Monitor Mozilla advisory pages for revisions or added guidance.
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-758: 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-2026-4724 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:H/A:N
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:N3.95.2Primary 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:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2014865CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-20/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-23/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.
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
Reliance on Undefined, Unspecified, or Implementation-Defined Behavior represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.