CVE-2026-4698Public exploitNetwork attack vector

Remote code execution via empty switch miscompilation

Published Mar 24, 2026 · Updated Mar 24, 2026

Type confusion in Firefox, Firefox ESR, and Thunderbird allows remote attackers to execute code through crafted JavaScript. IonMonkey's IsTrianglePattern accepts an MTableSwitch from an empty switch as an MGoto, causing out-of-bounds predecessor access after assertions are removed. Execution requires user interaction in Firefox before 149, Firefox ESR before 115.34 or 140.9, or Thunderbird before 149 or 140.9.

CVSS severity9.8
Critical
EPSS probability0.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Type confusion in Firefox, Firefox ESR, and Thunderbird allows remote attackers to execute code through crafted JavaScript. IonMonkey's IsTrianglePattern accepts an MTableSwitch from an empty switch as an MGoto, causing out-of-bounds predecessor access after assertions are removed. Execution requires user interaction in Firefox before 149, Firefox ESR before 115.34 or 140.9, or Thunderbird before 149 or 140.9.

The record

CVE
CVE-2026-4698
Published
Mar 24, 2026
Updated
Mar 24, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-843, CWE-733, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <149

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <149
Mozilla · Thunderbirdversion=unspecified <140.9; version=unspecified <149
Mozilla · Firefox ESRversion=unspecified <115.34; version=unspecified <140.9

Published CVSS scores

8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.5Red Hat SADPCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-843Access of Resource Using Incompatible Type ('Type Confusion')
CWE-733Compiler Optimization Removal or Modification of Security-critical Code
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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