CVE-2026-4716 | Incorrect boundary conditions, uninitialized memory in the JavaScript Engine component

Incorrect boundary conditions, uninitialized memory in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Published: 2026-03-24 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-4716 is rated Moderate Risk (48.1/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.41%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-4716

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.02% 0.41% +0.39%
2 2026-03-25 — 0.02% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4716

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.1 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.2 [email protected]
9.1 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.2 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-4716

OS Trackers for CVE-2026-4716

vendor priority summary link
alpine — CVE-2026-4716: 1 source package rows (firefox); 128 state rows across 2 repos (3.23-community, edge-community); fixed 0, open 128. https://security.alpinelinux.org/vuln/CVE-2026-4716
debian not yet assigned CVE-2026-4716 not yet assigned priority: Debian including 3 source packages (firefox, firefox-esr, thunderbird), 11 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 11. https://security-tracker.debian.org/tracker/CVE-2026-4716
redhat medium — https://access.redhat.com/security/cve/CVE-2026-4716
suse high CVE-2026-4716 severity important: SUSE including 34 source package names (MozillaFirefox-140.9.0-112.304.2, MozillaFirefox-140.9.0-150200.152.225.1, …), 116 product×package rows across 34 product lines (Image SLES15-SP5-SAP-Azure-LI-BYOS, Image SLES15-SP5-SAP-Azure-LI-BYOS-Production, … (34 product lines)): Fixed 112, First Fixed 4. https://www.suse.com/security/cve/CVE-2026-4716/
ubuntu medium CVE-2026-4716 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 40 status rows across 6 suites (bionic, focal, jammy, noble, questing, upstream): DNE 16, needs-triage 10, ignored 8, not-affected 5, needed 1. https://ubuntu.com/security/CVE-2026-4716

Affected software / configurations for CVE-2026-4716

Vendor Product Version Raw CPE
mozilla firefox < 140.9.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
mozilla firefox < 149.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*

References for CVE-2026-4716

cvelogic Threat Intelligence