Security readout for executives and security teams
Plain-English summary
CVE-2026-4718 is a high-severity Mozilla vulnerability in WebRTC signaling. Mozilla says it is fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The CVSS rating indicates a network-delivered issue requiring user interaction, with potential confidentiality and integrity impact. No provided source states active exploitation.
Executive priority
Prioritize normal emergency browser and mail-client patching. The issue is high severity with potential data exposure or tampering, but public evidence provided here does not show active exploitation. Focus on rapid update compliance across user endpoints.
Technical view
The CVE describes undefined behavior in the WebRTC: Signaling component, classified as CWE-758. CVSS 3.1 is 8.1: AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N. The source bundle does not provide exploit details. Fixed releases are listed for Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR.
Likely exposure
Organizations using Mozilla Firefox or Thunderbird below the fixed release levels may be exposed. Exposure is most relevant where users browse untrusted content or handle external communications. The bundle does not define exact affected version ranges beyond the fixed versions.
Exploitation context
The CVSS vector indicates remote network exposure, low attack complexity, no privileges required, and required user interaction. There is no KEV listing in the provided bundle and no cited source here claims exploitation in the wild.
Researcher notes
Mozilla’s public description is sparse: undefined behavior in WebRTC signaling with high confidentiality and integrity impact. Bugzilla may contain restricted details. Avoid assuming memory corruption mechanics, affected ranges, or exploitability beyond the CVSS and Mozilla fixed-release statements.
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 platform-specific deployment guidance.
Validation and detection
- Inventory deployed Firefox and Thunderbird versions.
- Confirm endpoints run the fixed release levels or newer.
- Check patch management reports for failed Mozilla updates.
- Monitor Mozilla advisories for any revised affected-version guidance.
- Document exceptions and prioritize internet-facing user populations.
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
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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
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Open ATT&CK lookupCVE-2026-4718 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
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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:R/S:U/C:H/I:H/A:N2.85.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2014864CVE 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.