Critical severity · published Mar 24, 2026
CVE-2026-4698
JIT miscompilation in the JavaScript Engine: JIT component
9.8
CVSS
0.8%
EPSS
No
On KEV
Description
JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 56% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 115.34.0; before 149.0; 128.0 before 140.9.0 · source: NVD
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 6 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 7 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 7 Extended Lifecycle Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.2 Advanced Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.6 Telecommunications Update Service · Red Hat
All versions, or not specified · source: CISA
In the news
VulnerabilityHigh
ZDI-26-252: Mozilla Firefox IonMonkey Switch Statement Optimization Type Confusion Remote Code Execution Vulnerability
This vulnerability allows remote attackers to execute arbitrary code on affected installations of Mozilla Firefox. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The ZDI has assigned a CVSS rating of 8.8. The following CVEs are assigned: CVE-2026-4698.
Apr 2, 2026·Zero Day Initiative
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4698
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-4698
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2020906
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-20/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-21/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-22/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-23/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-24/
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