CVE-2026-4698: JIT miscompilation in the JavaScript Engine: JIT component
Vulnerability summary
CVE-2026-4698 is a critical (CVSS 9.8) vulnerability in mozilla firefox. EPSS estimates a 0.78% chance of exploitation in the next 30 days, higher than 56.1% of scored vulnerabilities.
Not severe (CVSS 8.8, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 39 · Related 9Timeline
- 24-03-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
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 metrics
4 scores · 4 sources · 1 version- CVE.orgCNA8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HDiffers
- OSV · UbuntuEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HDiffers
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.78%
Chance of exploitation in the next 30 days
Percentile
56%
Versus all other CVEs
30-day change
Increase +0.03 pp
From 0.76% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-843Access of Resource Using Incompatible TypeThe product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
- CWE-733Compiler Optimization Removal or Modification of Security-critical CodeThe developer builds a security-critical protection mechanism into the software, but the compiler optimizes the program such that the mechanism is removed or modified.
Affected systems
Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu8 products
- mozjs102All versions (No fix recorded)
- mozjs115All versions (No fix recorded)
- mozjs38All versions (No fix recorded)
- mozjs52All versions (No fix recorded)
- mozjs68All versions (No fix recorded)
Chainguard2 products
- firefox< 149.0-r0
- firefox-esr< 140.9.0-r0
Debian2 products
- firefox-esr< 140.9.0esr-1~deb12u1 | < 140.9.0esr-1~deb13u1 | < 140.9.0esr-1
- thunderbird< 1:140.9.0esr-1~deb12u1 | < 1:140.9.0esr-1~deb13u1 | < 1:140.9.0esr-1
Mozilla1 product
- firefox< 115.34.0 | < 149.0 | ≥ 128.0, < 140.9.0
Wolfi1 product
- firefox< 149.0-r0
5 vendors · 14 products
