CVE-2026-4689 | Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component

Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, 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-2026-4689 is rated Moderate Risk (40.2/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.01%). 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-2026-4689

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 2026-03-25 — 0.01% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4689

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
10.0 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/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:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 6.0 [email protected]
10.0 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/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:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 6.0 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-4689

OS Trackers for CVE-2026-4689

vendor priority summary link
alpine — CVE-2026-4689: 2 source package rows (firefox, thunderbird); 180 state rows across 2 repos (3.23-community, edge-community); fixed 0, open 180. https://security.alpinelinux.org/vuln/CVE-2026-4689
debian not yet assigned CVE-2026-4689 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-2026-4689
redhat high — https://access.redhat.com/security/cve/CVE-2026-4689
suse high CVE-2026-4689 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-2026-4689/
ubuntu medium CVE-2026-4689 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-2026-4689

Affected software / configurations for CVE-2026-4689

Vendor Product Version Raw CPE
mozilla firefox < 115.34.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
mozilla firefox < 149.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
mozilla firefox >= 128.0, < 140.9.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
mozilla thunderbird < 140.9.0 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
mozilla thunderbird < 149.0 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

References for CVE-2026-4689

cvelogic Threat Intelligence