Security readout for executives and security teams
Plain-English summary
CVE-2026-2783 is a Mozilla browser and mail client flaw where a JavaScript engine JIT compiler error could expose information. A user would likely need to open or view attacker-controlled content. Mozilla says it is fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Executive priority
Treat as a normal priority endpoint patching item. It can expose sensitive data, but sources indicate user interaction is required and do not show active exploitation. Ensure Mozilla desktop applications are updated during the next standard security update cycle, sooner for high-risk users.
Technical view
The vulnerability is CWE-200 information disclosure caused by JIT miscompilation in Mozilla’s JavaScript Engine JIT component. CVSS 3.1 is 6.5: network-reachable, low complexity, no privileges required, user interaction required, high confidentiality impact, no integrity or availability impact.
Likely exposure
Organizations using Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR below the Mozilla fixed releases may be exposed, especially where users browse untrusted sites or open HTML-capable email content. The provided sources do not identify specific affected pre-fix version ranges.
Exploitation context
The CVSS vector requires user interaction, so exploitation likely depends on convincing a user to load malicious web or message content. The source bundle does not report public exploitation, and CISA KEV status is false.
Researcher notes
Key uncertainty: the bundle names fixed releases but does not provide detailed vulnerable version ranges. Bugzilla details may be restricted or limited. Avoid assuming code execution; the stated impact is information disclosure only.
Mitigation direction
- Upgrade Firefox to 148 or later where applicable.
- Upgrade Firefox ESR to 140.8 or later.
- Upgrade Thunderbird to 148 or later where applicable.
- Upgrade Thunderbird ESR to 140.8 or later.
- Review Mozilla advisories for product-specific guidance and deployment notes.
Validation and detection
- Inventory installed Firefox and Thunderbird versions across endpoints.
- Confirm versions meet or exceed Mozilla’s fixed releases.
- Check patch management records for successful browser and mail client updates.
- Prioritize systems used for internet browsing or external email handling.
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-200: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. 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-2026-2783 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
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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:N/A:N2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2010943CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-13/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-15/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-16/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-17/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.
Exposure of Sensitive Information to an Unauthorized Actor
Exposure of Sensitive Information to an Unauthorized Actor represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.