Security readout for executives and security teams
Plain-English summary
Mozilla fixed multiple memory safety bugs in Firefox 134 and Thunderbird 134. The reported bugs were present in Firefox 133 and Thunderbird 133 and showed memory corruption. Mozilla states some could likely be exploited to run arbitrary code with enough effort.
Executive priority
Treat as an urgent client software update. No active exploitation is cited, but critical memory corruption in widely used browser and mail clients creates meaningful business risk if version 133 remains deployed.
Technical view
CVE-2025-0247 covers memory safety defects affecting Firefox 133 and Thunderbird 133, fixed in version 134. The CVSS 3.1 score is 9.8 critical, with high confidentiality, integrity, and availability impact. No CWE is listed in the provided sources.
Likely exposure
Organizations with Firefox 133 or Thunderbird 133 deployed before upgrading to 134 are the likely exposed population. The source bundle’s affected metadata lists 134, but the description says the bugs were present in 133 and fixed in 134.
Exploitation context
The provided KEV flag is false, and the cited sources do not state active exploitation. Mozilla’s advisory language indicates memory corruption and a presumption that arbitrary code execution may be possible with enough effort.
Researcher notes
The sources do not provide exploit details, affected platforms, or component-level root cause beyond grouped Mozilla bug references. Treat this as an aggregate memory safety advisory and validate exposure primarily by product version.
Mitigation direction
- Update Firefox and Thunderbird to version 134 or later.
- Confirm automatic updates are enabled across managed endpoints.
- Remove or isolate unmanaged version 133 installations until upgraded.
- Review Mozilla advisories for any product-specific follow-up guidance.
Validation and detection
- Inventory installed Firefox and Thunderbird versions across endpoints.
- Confirm no Firefox 133 or Thunderbird 133 installations remain.
- Validate update status through endpoint management or product version reporting.
- Track scanner results against CVE-2025-0247 after patch deployment.
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
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Execution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2025-0247 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.
SSVC decision data
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:H/I:H/A:H3.95.9CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Memory safety bugs fixed in Firefox 134 and Thunderbird 134CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2025-01/CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2025-04/CVE reference, mozilla
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.