Security readout for executives and security teams
Plain-English summary
CVE-2026-0887 is a Mozilla PDF Viewer issue where a user could be tricked through clickjacking into exposing limited information. It requires user interaction and affects confidentiality only. Mozilla states it was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.
Executive priority
Treat as routine but time-bound patching. The business risk is limited information disclosure, not system takeover, but broad desktop exposure can make delayed updates risky. Include it in the next browser and mail-client update cycle.
Technical view
The vulnerability is described as clickjacking-based information disclosure in Mozilla’s PDF Viewer component. CVSS 3.1 is 4.3: network attack vector, low complexity, no privileges, user interaction required, low confidentiality impact, no integrity or availability impact. It maps to CWE-497.
Likely exposure
Organizations using Mozilla Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR before the fixed releases may be exposed when users open or interact with PDFs in vulnerable contexts. Exposure is higher where browsers or mail clients are not centrally updated.
Exploitation context
The source bundle does not indicate active exploitation, and the CVE is not listed as CISA KEV. Successful exploitation requires user interaction, consistent with clickjacking. Public details are limited in the provided sources, so exploitability should not be overstated.
Researcher notes
Mozilla’s public description is concise and does not include detailed proof-of-concept information in the provided bundle. Analysis should focus on version validation, PDF Viewer exposure, and advisory tracking rather than assuming broader impact.
Mitigation direction
- Update Firefox to version 147 or later.
- Update Firefox ESR to version 140.7 or later.
- Update Thunderbird to version 147 or later.
- Update Thunderbird ESR to version 140.7 or later.
- Check Mozilla advisories for any deployment-specific guidance.
Validation and detection
- Inventory Firefox and Thunderbird versions across endpoints.
- Confirm installed versions meet or exceed Mozilla’s fixed releases.
- Review endpoint management compliance for browser and mail-client updates.
- Prioritize users who frequently handle PDFs from external sources.
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-497: 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-2026-0887 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
- 4.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/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:L/I:N/A:N2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2006500CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-01/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-03/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-04/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-05/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 System Information to an Unauthorized Control Sphere
Exposure of Sensitive System Information to an Unauthorized Control Sphere represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.