Security readout for executives and security teams
Plain-English summary
Firefox contained a flaw in certain canvas operations that could corrupt memory. The supplied CVSS score is 9.8, indicating potentially severe confidentiality, integrity, and availability consequences. Mozilla states the vulnerability was fixed in Firefox 139.0.4.
Executive priority
Treat remediation as urgent because the supplied severity is critical and Firefox may process untrusted web content. Direct teams to establish version coverage and deploy the fixed release promptly. Do not characterize this as an active-exploitation emergency without additional evidence.
Technical view
CVE-2025-49709 is a canvas-surface memory-corruption vulnerability categorized as CWE-787. Its CVSS vector describes network accessibility, low attack complexity, no required privileges or user interaction, and high impact across confidentiality, integrity, and availability. The sources do not establish a specific resulting capability such as code execution.
Likely exposure
Firefox installations not yet updated to the fixed release are the primary concern. However, the bundle’s affected-version field lists 139.0.4 while its description says 139.0.4 contains the fix. Confirm the authoritative affected range with Mozilla before finalizing exposure counts.
Exploitation context
The supplied bundle marks this CVE as absent from CISA KEV, and no included source states that it is actively exploited. The critical CVSS assessment indicates serious theoretical risk, but observed exploitation, exploit availability, and attack prevalence are not established here.
Researcher notes
The public description provides limited root-cause detail beyond canvas operations and memory corruption. Bugzilla may contain additional technical context, but none is reproduced in the bundle. The conflicting affected-version metadata materially limits precise exposure assessment; 139.0.4 should be treated as the stated fixed version pending vendor confirmation.
Mitigation direction
- Update Firefox to version 139.0.4 or later through approved software-management channels.
- Prioritize endpoints that still run releases older than the stated fixed version.
- Consult Mozilla’s advisory for any revised affected-version or remediation guidance.
- Apply compensating restrictions based on vendor guidance if immediate updating is impossible.
Validation and detection
- Inventory Firefox versions across managed endpoints and identify installations below 139.0.4.
- Confirm updated endpoints report Firefox 139.0.4 or later.
- Review deployment failures and approved update exceptions until remaining exposure is understood.
- Reconcile scanner findings against Mozilla’s authoritative affected-version information.
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-787: 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-2025-49709 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
- https://bugzilla.mozilla.org/show_bug.cgi?id=1966083CVE reference, mozilla
- https://www.mozilla.org/security/advisories/mfsa2025-47/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.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.