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CVE-2026-5734 Details

Description

Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.

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: redhat-SADPCVSS-B:8.8 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://access.redhat.com/errata/RHSA-2026:11805	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:11813	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:12264	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13342	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13412	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13533	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13582	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13583	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13596	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13600	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13665	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13682	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13683	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13922	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:13977	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:14223	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:14303	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:15889	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:7671	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:7672	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:8052	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:8459	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:9345	redhat-SADP
https://access.redhat.com/errata/RHSA-2026:9638	redhat-SADP
https://access.redhat.com/security/cve/CVE-2026-5734	redhat-SADP
https://bugzilla.redhat.com/show_bug.cgi?id=2455897	redhat-SADP
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5734.json	redhat-SADP
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2022369%2C2023026%2C2023545%2C2023555%2C2023958%2C2025422%2C2025468%2C2025492%2C2025505	[email protected]	Broken LinkIssue Tracking
https://www.mozilla.org/security/advisories/mfsa2026-25/	[email protected]	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-27/	[email protected]	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-28/	[email protected]
https://www.mozilla.org/security/advisories/mfsa2026-29/	[email protected]

see all 32 references

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-787	Out-of-bounds Write	[email protected]
CWE-120	Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')	CISA-ADP
CWE-787	Out-of-bounds Write	redhat-SADP

Affected Products

Product	Versions
mozilla firefox	< 140.9.1 < 149.0.2
CPE cpe:2.3:a:mozilla:firefox:::::esr:::* cpe:2.3:a:mozilla:firefox:::::-:::* Remediation No remediation found in references.
mozilla thunderbird	< 140.9.1 < 149.0.2
CPE cpe:2.3:a:mozilla:thunderbird:::::esr:::* cpe:2.3:a:mozilla:thunderbird:::::-:::* Remediation No remediation found in references.

Change History

9 change records found show changes

Date	Action	Recorded By
Jul 15, 2026	CVE Modified	redhat-SADP
Jun 30, 2026	CVE Modified	redhat-SADP
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Apr 13, 2026	CVE Modified	[email protected]
Apr 13, 2026	CVE Modified	CISA-ADP
Apr 7, 2026	CVE Modified	[email protected]
Apr 7, 2026	Initial Analysis	[email protected]
Apr 7, 2026	New CVE Received	[email protected]