CVE-2026-4700 | Mitigation bypass in the Networking: HTTP component

Mitigation bypass in the Networking: HTTP 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-2026-4700 is rated Moderate Risk (40.7/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.02%). 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-2026-4700

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 — 0.02% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4700

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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: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: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 5.9 [email protected]
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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: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: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 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-4700

OS Trackers for CVE-2026-4700

vendor priority summary link
alpine — CVE-2026-4700: 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-2026-4700
debian not yet assigned CVE-2026-4700 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-2026-4700
redhat high — https://access.redhat.com/security/cve/CVE-2026-4700
suse high CVE-2026-4700 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-2026-4700/
ubuntu medium CVE-2026-4700 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-2026-4700

Affected software / configurations for CVE-2026-4700

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-2026-4700

cvelogic Threat Intelligence