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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00588.

Exploitation none

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Mozilla Firefox affected
Version Status Constraints
135 unaffected ≤ *
Mozilla Thunderbird affected
Version Status Constraints
135 unaffected ≤ *

Configuration 1 [-]

OR cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

No data.

No data.

Project Subscriptions

Vendors Products
Mozilla Subscribe
Firefox Subscribe
Thunderbird Subscribe
Advisories
Source ID Title
EUVD EUVD EUVD-2025-1975 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 affects Firefox < 135 and Thunderbird < 135.
Ubuntu USN Ubuntu USN USN-7263-1 Firefox vulnerabilities
Ubuntu USN Ubuntu USN USN-7991-1 Thunderbird vulnerabilities
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1939063%2C1942169 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2025-1020 cve-icon
https://www.cve.org/CVERecord?id=CVE-2025-1020 cve-icon
https://www.mozilla.org/security/advisories/mfsa2025-07/ cve-icon cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2025-11/ cve-icon cve-icon cve-icon
History

Mon, 13 Apr 2026 15:00:00 +0000

Type Values Removed Values Added
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 affects Firefox < 135 and Thunderbird < 135. 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.
Title firefox: thunderbird: Memory safety bugs fixed in Firefox 135 and Thunderbird 135 Memory safety bugs fixed in Firefox 135 and Thunderbird 135

Tue, 15 Jul 2025 13:45:00 +0000

Type Values Removed Values Added
Metrics epss

{'score': 0.00149}

 epss

{'score': 0.00189}

Fri, 07 Feb 2025 14:30:00 +0000

Type Values Removed Values Added
Title firefox: thunderbird: Memory safety bugs fixed in Firefox 135 and Thunderbird 135
Weaknesses CWE-120
References
Metrics threat_severity

None

 threat_severity

Important

Thu, 06 Feb 2025 21:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Thu, 06 Feb 2025 20:00:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Mozilla thunderbird
Weaknesses CWE-787
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*
Vendors & Products Mozilla
Mozilla firefox
Mozilla thunderbird
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Tue, 04 Feb 2025 14:15:00 +0000

Type Values Removed Values Added
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 affects Firefox < 135 and Thunderbird < 135.
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-04-13T14:25:25.512Z

Reserved: 2025-02-04T07:26:48.228Z

Link: CVE-2025-1020

cve-icon Vulnrichment

Updated: 2025-02-06T21:06:58.354Z

cve-icon NVD

Status : Modified

Published: 2025-02-04T14:15:32.953

Modified: 2026-04-13T15:16:51.213

Link: CVE-2025-1020

cve-icon Redhat

Severity : Important

Publid Date: 2025-02-04T13:58:56Z

Links: CVE-2025-1020 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses