CVE-2025-4093

Memory safety bug fixed in Firefox ESR 128.10 and Thunderbird 128.10

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Published Apr 29, 2025 CVSS 3.1 · 8.1 High EPSS < 1% KEV · Not listed
Description
Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.10 and Thunderbird 128.10.

Analysis

AI-generated

Technical impact

The vulnerability is a memory safety bug that existed in Firefox ESR 128.9 and Thunderbird 128.9, causing memory corruption that could be leveraged to run arbitrary code. It represents a buffer overflow and classic buffer overrun weakness (CWE-119, CWE-120) and has a CVSS score of 8.1, indicating high severity.

Affected Systems

Affected products are Mozilla Firefox ESR and Thunderbird ESR. All releases prior to 128.10 are impacted, including 128.9. The bug is relevant to installations on systems identified by the supplied CPE strings, such as Red Hat Enterprise Linux 8 and 9 and their extended support variants.

Risk and Exploitability

The EPSS score is less than 1%, indicating a low current exploitation probability, and the vulnerability is not listed in CISA’s KEV catalog. The most likely attack path is remote, involving malicious content rendered by the browser—such as a crafted web page or a deceptive email—to trigger the memory corruption and potentially execute arbitrary code. No public exploit is known, but the high CVSS score warrants proactive mitigation.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade Firefox ESR to 128.10 or a later version, and upgrade Thunderbird ESR to 128.10 or later, which contain the patch for this memory safety bug.
  • Enable automatic updates for Firefox ESR and Thunderbird ESR so that future security fixes are applied without user intervention.
  • If an immediate upgrade is not feasible, limit the use of these browsers for potentially untrusted content, disable native plugins or features that execute native code, and monitor for anomalous activity that could indicate exploitation attempts.

Generated by OpenCVE AI on April 20, 2026 at 17:11 UTC.

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4167-1 thunderbird security update
Debian DLA Debian DLA DLA-4172-1 firefox-esr security update
Debian DSA Debian DSA DSA-5910-1 firefox-esr security update
Debian DSA Debian DSA DSA-5912-1 thunderbird security update
EUVD EUVD EUVD-2025-12642 Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 128.10 and Thunderbird < 128.10.
Ubuntu USN Ubuntu USN USN-7663-1 Thunderbird vulnerabilities
History
Type Values Removed Values Added
Description Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 128.10 and Thunderbird < 128.10. Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.10 and Thunderbird 128.10.
Title firefox: thunderbird: Memory safety bug fixed in Firefox ESR 128.10 and Thunderbird 128.10 Memory safety bug fixed in Firefox ESR 128.10 and Thunderbird 128.10
Type Values Removed Values Added
References
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}

 cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'}
Type Values Removed Values Added
First Time appeared Redhat rhel Aus
Redhat rhel Tus
CPEs cpe:/a:redhat:rhel_aus:8.2
cpe:/a:redhat:rhel_aus:8.4
cpe:/a:redhat:rhel_aus:8.6
cpe:/a:redhat:rhel_e4s:8.4
cpe:/a:redhat:rhel_e4s:8.6
cpe:/a:redhat:rhel_eus:8.8
cpe:/a:redhat:rhel_tus:8.4
cpe:/a:redhat:rhel_tus:8.6
Vendors & Products Redhat rhel Aus
Redhat rhel Tus
Type Values Removed Values Added
CPEs cpe:/o:redhat:enterprise_linux:10.0
Type Values Removed Values Added
CPEs cpe:/a:redhat:rhel_eus:9.4
Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Mozilla thunderbird
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
Vendors & Products Mozilla
Mozilla firefox
Mozilla thunderbird
Type Values Removed Values Added
First Time appeared Redhat rhel E4s
Redhat rhel Els
Redhat rhel Eus
CPEs cpe:/a:redhat:rhel_e4s:9.0
cpe:/a:redhat:rhel_eus:9.2
cpe:/o:redhat:rhel_els:7
Vendors & Products Redhat rhel E4s
Redhat rhel Els
Redhat rhel Eus
Type Values Removed Values Added
First Time appeared Redhat
Redhat enterprise Linux
CPEs cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Type Values Removed Values Added
Title firefox: thunderbird: Memory safety bug fixed in Firefox ESR 128.10 and Thunderbird 128.10
Weaknesses CWE-120
References
Metrics threat_severity

None

 threat_severity

Important
Type Values Removed Values Added
Description Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 128.10 and Thunderbird ESR < 128.10. Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 128.10 and Thunderbird < 128.10.
Type Values Removed Values Added
Weaknesses CWE-119
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}
Type Values Removed Values Added
Description Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 128.10 and Thunderbird ESR < 128.10.
References
Earlier changes (8)
Weaknesses
  • CWE-119

    Improper Restriction of Operations within the Bounds of a Memory Buffer

  • CWE-120

    Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Sources

Status
PUBLISHED
Assigner
mozilla
Published
Updated
Apr 13, 2026, 2:27 PM
Reserved
Apr 29, 2025, 1:13 PM

View source JSON

Updated
Nov 3, 2025, 7:58 PM

JSON

Status
Modified
Published
Apr 29, 2025, 2:15 PM
Modified
Oct 5, 2026, 3:10 PM

View source JSON

Severity
Important
Public date
Apr 29, 2025, 1:13 PM

View source Bugzilla JSON

Updated
Apr 20, 2026, 5:15 PM

JSON