Security readout for executives and security teams
Plain-English summary
CVE-2026-4727 is a denial-of-service issue in Mozilla’s NSS libraries component. Mozilla says it was fixed in Firefox 149 and Thunderbird 149. The main business risk is service or application disruption, not data theft or system takeover based on the provided CVSS metrics.
Executive priority
Prioritize normal-to-expedited patching where Firefox or Thunderbird are broadly deployed. Treat as availability risk: disruption is the expected impact in the provided record, not confirmed data compromise. Escalate if critical business workflows depend on affected clients.
Technical view
The CVE is classified as CWE-400 resource consumption. CVSS 3.1 is 7.5: network-reachable, low complexity, no privileges, no user interaction, high availability impact, and no confidentiality or integrity impact. The source bundle does not provide affected version ranges beyond the Mozilla fix statements.
Likely exposure
Organizations using Firefox or Thunderbird builds before the Mozilla-fixed releases may be exposed. Exposure depends on deployed versions and whether NSS functionality is reachable in the organization’s usage. The provided data does not identify other NSS-consuming products as affected.
Exploitation context
No CISA KEV listing is indicated, and the provided sources do not state active exploitation. The CVSS vector suggests remote denial-of-service may be possible without authentication or user interaction, but exploit details are not included in the source bundle.
Researcher notes
Key gap: the bundle says fixed in Firefox 149 and Thunderbird 149 but does not provide full vulnerable version ranges. Do not assume other NSS consumers are affected without vendor confirmation. Bugzilla and Mozilla advisories are the primary references for further triage.
Mitigation direction
- Update Firefox to version 149 or later, following Mozilla guidance.
- Update Thunderbird to version 149 or later, following Mozilla guidance.
- Inventory systems using Mozilla Firefox and Thunderbird.
- Monitor Mozilla advisories for any expanded affected-version guidance.
Validation and detection
- Confirm Firefox versions installed across managed endpoints.
- Confirm Thunderbird versions installed across managed endpoints.
- Verify patched systems report version 149 or later.
- Review vulnerability scanner results against Mozilla advisory references.
- Check exception lists for systems unable to update promptly.
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-2026-4727 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=2008112CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-20/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-23/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.