Security readout for executives and security teams
Plain-English summary
CVE-2026-4705 is a critical Mozilla vulnerability in the WebRTC signaling component. Mozilla says it is fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The public record rates it 9.8, meaning successful exploitation could severely affect confidentiality, integrity, and availability. No provided source confirms active exploitation.
Executive priority
Treat as urgent patching for managed browsers and email clients. The severity is critical and the scoring suggests high potential impact, but no provided source confirms active exploitation. Prioritize rapid update verification across endpoint fleets.
Technical view
The issue is described as undefined behavior in WebRTC: Signaling and mapped to CWE-758. CVSS 3.1 is 9.8 with network attack vector, low complexity, no privileges, no user interaction, unchanged scope, and high CIA impact. Public sources do not provide deeper root-cause or exploitability details.
Likely exposure
Exposure is likely where Mozilla Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR are below the fixed versions named by Mozilla. Internet-connected endpoints using these products should be prioritized. The provided sources do not identify affected operating systems, configurations, or downstream products.
Exploitation context
The CVSS vector indicates potential remote exploitation without authentication or user interaction. However, the source bundle does not include exploit details, proof-of-concept availability, or confirmed in-the-wild exploitation. CISA KEV status is false in the provided data.
Researcher notes
Public detail is limited to undefined behavior in WebRTC signaling and CWE-758. Avoid assuming memory corruption mechanics or exploit primitives without Mozilla details. Bugzilla and Mozilla advisories are the primary references for further updates.
Mitigation direction
- Update Firefox to 149 or later where applicable.
- Update Firefox ESR to 140.9 or later.
- Update Thunderbird to 149 or later where applicable.
- Update Thunderbird ESR to 140.9 or later.
- Review Mozilla advisories for product-specific deployment guidance.
Validation and detection
- Inventory deployed Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR versions.
- Confirm endpoints are at or above Mozilla’s fixed versions.
- Check software management tools for failed or deferred updates.
- Monitor Mozilla advisories for any updated technical guidance.
- Document exceptions and prioritize remediation of internet-facing or high-risk endpoints.
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-2026-4705 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=2014873CVE 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.
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.