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CVE-2025-1020 Details

Description

Memory safety bugs present in Firefox 134 and Thunderbird 134. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 135 and Thunderbird 135.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:9.8 CRITICALVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CNA: CISA-ADPCVSS-B:9.8 CRITICALVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1939063%2C1942169	[email protected]	Broken Link
https://www.mozilla.org/security/advisories/mfsa2025-07/	[email protected]	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-11/	[email protected]	Vendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-787	Out-of-bounds Write	[email protected]
CWE-787	Out-of-bounds Write	CISA-ADP

Affected Products

Product	Versions
mozilla firefox	< 135.0
CPE cpe:2.3:a:mozilla:firefox:::::-:::* Remediation No remediation found in references.
mozilla thunderbird	>= 131.0, < 135.0
CPE cpe:2.3:a:mozilla:thunderbird:::::-:::* Remediation No remediation found in references.

Change History

6 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Apr 13, 2026	CVE Modified	[email protected]
Feb 6, 2025	CVE Modified	CISA-ADP
Feb 6, 2025	Initial Analysis	[email protected]
Feb 4, 2025	New CVE Received	[email protected]