Security readout for executives and security teams
Plain-English summary
CVE-2026-0889 is a Mozilla denial-of-service flaw in the DOM Service Workers component. Mozilla says it was fixed in Firefox 147 and Thunderbird 147. The business impact is availability: a vulnerable browser or mail client could be forced to stop responding or crash, disrupting users rather than exposing data.
Executive priority
Treat as a prompt endpoint patching item, especially for large Firefox or Thunderbird deployments. It is high severity due to availability impact, but current provided sources do not indicate active exploitation or compromise of sensitive data.
Technical view
The CVE is mapped to CWE-400 and carries CVSS 3.1 score 7.5: network-accessible, low complexity, no privileges, no user interaction, unchanged scope, and high availability impact only. Sources identify the affected component as DOM: Service Workers and name Firefox and Thunderbird fixes in version 147.
Likely exposure
Organizations with Firefox or Thunderbird below the Mozilla fixed releases are the likely exposure group. Exposure is most relevant on endpoints where these applications are installed and can process remote web or message content that reaches the vulnerable component.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. Public information provided here supports a remotely reachable denial-of-service risk, not data theft, privilege escalation, or code execution.
Researcher notes
Evidence is limited to the CVE description, Mozilla advisories, and Bugzilla reference. The root-cause details are not included in the supplied text. Focus validation on version exposure and availability symptoms; avoid assuming confidentiality or integrity impact beyond the CVSS vector.
Mitigation direction
- Update Firefox to version 147 or a later vendor-supported release.
- Update Thunderbird to version 147 or a later vendor-supported release.
- Prioritize managed endpoints, shared workstations, and high-availability user roles.
- Check Mozilla advisories for any revised guidance or backported fixes.
Validation and detection
- Inventory installed Firefox and Thunderbird versions across endpoints.
- Confirm deployed versions meet or exceed Mozilla’s fixed release information.
- Review endpoint telemetry for unusual browser or Thunderbird crashes.
- Track Mozilla advisory updates and the linked Bugzilla record.
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-400: 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-2026-0889 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
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.
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:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=1999084CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-01/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-04/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.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.