Security readout for executives and security teams
Plain-English summary
CVE-2026-0890 is a medium-severity Mozilla issue involving spoofing in DOM copy/paste and drag-and-drop handling. A malicious web or message interaction could mislead a user and cause limited confidentiality impact and some availability impact. Mozilla says it is fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.
Executive priority
Schedule routine but timely browser and mail-client updates. This is not marked as actively exploited, but it affects common user-facing software and depends on social interaction, making broad endpoint patch compliance the main business control.
Technical view
The CVE describes a CWE-290 spoofing flaw in Mozilla’s DOM Copy & Paste and Drag & Drop component. CVSS 3.1 is 5.4: network reachable, low complexity, no privileges, user interaction required, with low confidentiality and availability impact. The public bundle does not provide detailed root-cause or proof-of-concept information.
Likely exposure
Organizations using Firefox, Firefox ESR, Thunderbird, or Thunderbird ESR below the Mozilla-fixed releases should treat endpoints as potentially exposed. Exposure depends on user interaction with crafted web content or content handled through Thunderbird. The source bundle does not identify server-side exposure.
Exploitation context
No active exploitation is indicated in the provided sources, and the CVE is not listed as CISA KEV in the bundle. Exploitation requires user interaction, reducing urgency compared with unauthenticated remote code execution, but browser and mail-client issues still warrant timely patching.
Researcher notes
Public details are sparse. The CVE names DOM copy/paste and drag-and-drop spoofing and provides CVSS but not exploit mechanics. Avoid assuming code execution or broader product impact. Use Mozilla advisories and Bugzilla entry for any later technical clarification.
Mitigation direction
- Update Firefox to 147 or later where applicable.
- Update Firefox ESR to 140.7 or later.
- Update Thunderbird to 147 or later where applicable.
- Update Thunderbird ESR to 140.7 or later.
- Review Mozilla advisories for environment-specific guidance.
Validation and detection
- Inventory installed Firefox and Thunderbird versions across endpoints.
- Confirm versions meet or exceed Mozilla’s fixed releases.
- Prioritize users who browse untrusted sites or handle external email.
- Check patch-management reports for failed or deferred updates.
- Monitor Mozilla advisories for any revised affected-version details.
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-290: 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-2026-0890 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
- 5.4 (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:L
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:L2.82.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.4MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=2005081CVE 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.
Authentication Bypass by Spoofing
Authentication Bypass by Spoofing represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.