CVE-2019-9794
A vulnerability was discovered where specific command line arguments are not properly discarded during Firefox invocation as a shell handler for URLs.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.77%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
A vulnerability was discovered where specific command line arguments are not properly discarded during Firefox invocation as a shell handler for URLs. This could be used to retrieve and execute files whose location is supplied through these command line arguments if Firefox is configured as the default URI handler for a given URI scheme in third party applications and these applications insufficiently sanitize URL data. *Note: This issue only affects Windows operating systems. Other operating systems are unaffected.*. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.
- CVSS 3.0
- 9.8 CRITICALCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 1.77% probability · 78th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-88
- Affected
- mozilla/firefox · mozilla/thunderbird
- Source
- security@mozilla.org
EPSS 1.8% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1530103Issue Tracking, Permissions Required, Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2019-07/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2019-08/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2019-11/Vendor Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1530103Issue Tracking, Permissions Required, Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2019-07/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2019-08/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2019-11/Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.