Security readout for executives and security teams
Plain-English summary
CVE-2026-2786 is a high-severity Mozilla JavaScript engine memory safety flaw. A user could be exposed through web or message content that causes Firefox or Thunderbird to process JavaScript. Mozilla says it was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Executive priority
Treat as a near-term desktop patching priority. It affects widely deployed user-facing software and has high confidentiality, integrity, and availability impact, but the bundle does not indicate known active exploitation.
Technical view
The issue is a CWE-416 use-after-free in Mozilla's JavaScript Engine component. CVSS 3.1 is 8.8, with network attack vector, low complexity, no privileges required, and user interaction required. Impact is rated high for confidentiality, integrity, and availability.
Likely exposure
Exposure is most likely on endpoints running Firefox or Thunderbird that have not been updated to the Mozilla fixed releases named in the CVE record and advisories.
Exploitation context
The provided bundle does not show CISA KEV listing or any cited evidence of active exploitation. The CVSS vector indicates remote content plus user interaction, but no exploit details are provided.
Researcher notes
Available evidence identifies a JavaScript engine use-after-free and fixed Mozilla release lines, but does not provide technical root cause details. Avoid assuming exploitability beyond the CVSS vector and Mozilla advisory language.
Mitigation direction
- Update Firefox to version 148 or Firefox ESR 140.8 where applicable.
- Update Thunderbird to version 148 or Thunderbird 140.8 where applicable.
- Prioritize managed desktop and email-client fleets with delayed browser updates.
- Check Mozilla advisories for platform-specific packaging and deployment guidance.
Validation and detection
- Inventory Firefox and Thunderbird versions across managed endpoints.
- Compare installed versions against Mozilla fixed releases named in the advisories.
- Confirm ESR users are on Firefox ESR 140.8 or Thunderbird 140.8.
- Review vulnerability scanner results for CVE-2026-2786 after patch deployment.
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-2026-2786 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
- 8.8 (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: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.
SSVC decision data
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:H2.85.9CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2013612CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-13/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-15/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-16/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2026-17/CVE reference, mozilla
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.