Security readout for executives and security teams
Plain-English summary
This flaw could let a locally opened page in old Firefox infer whether a named file exists on the user’s machine. It is an information-disclosure issue, not a remote takeover in the provided sources. Business urgency is mainly legacy-browser cleanup and reducing exposure to untrusted local HTML content.
Executive priority
Treat this as a legacy hygiene issue unless old Firefox remains in production. It is low urgency for modern fleets, but any confirmed Firefox below 51 should be remediated because browser vulnerabilities accumulate and unsupported software is difficult to defend.
Technical view
CVE-2017-5387 affects Firefox before 51. When a locally loaded page uses a media track source that points to a missing local file, duplicate error behavior can reveal whether a specifically requested local file exists. The bundle provides no CVSS score, CWE, active exploitation, or detailed fix text beyond the affected version boundary.
Likely exposure
Exposure is most likely on endpoints still running Firefox older than version 51, especially where users can open untrusted local HTML files. Modern, supported Firefox deployments should not be exposed based on the affected-version statement.
Exploitation context
The source bundle does not show KEV listing or active exploitation. The issue requires a locally loaded source page and only supports local file-existence inference, based on the CVE description provided.
Researcher notes
Evidence is concise and incomplete: no CVSS, CWE, exploit status, or detailed remediation text is present in the bundle. The core condition is local-page context in Firefox before 51 with observable error behavior that leaks existence of a requested local file.
Mitigation direction
- Upgrade Firefox to version 51 or later, because sources identify Firefox before 51 as affected.
- Remove unsupported Firefox versions from managed endpoints.
- Limit user handling of untrusted local HTML files on legacy systems.
- Check Mozilla advisory guidance before relying on compensating controls.
Validation and detection
- Inventory Firefox versions and flag any endpoint below version 51.
- Confirm vulnerability scanners detect or exclude obsolete Firefox installations accurately.
- Review endpoint software allowlists for unsupported Firefox binaries.
- Check whether users can open untrusted local HTML in vulnerable browsers.
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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CVE-2017-5387 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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 and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.mozilla.org/security/advisories/mfsa2017-01/CVE reference · x_refsource_CONFIRM
- https://bugzilla.mozilla.org/show_bug.cgi?id=1295023CVE reference · x_refsource_CONFIRM
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.