Mozilla Firefox EUVD-2026-98513

Exploitation requires the victim to actively load attacker-controlled web content in Firefox (UI:R) - for example by visiting a malicious or compromised site - so this cannot be triggered without user interaction and cannot be mass-automated (SSVC Automatable=no). No authentication or prior privileges are needed on the target (PR:N), and no non-default configuration is indicated by the description; the flaw lies in the default Networking component of Firefox. The impact is limited to disclosure of some confidential information (C:L) with no integrity or availability effect, and the fix is simply upgrading to Firefox 158 or Firefox ESR 153.5.

This is a genuinely low-to-moderate priority issue, and the available signals are largely consistent. The CVSS 3.1 base score of 4.3 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N) describes a network-reachable, low-complexity, unauthenticated flaw that nonetheless requires user interaction and yields only a limited confidentiality impact with no integrity or availability effect - consistent with CWE-200 information disclosure in Firefox's Networking component. CISA's SSVC framework reinforces the modest rating: Exploitation=none (no observed or public exploitation), Automatable=no (the UI:R requirement means it cannot be mass-scripted at scale), and Technical Impact=partial (matching C:L). The vulnerability is NOT on the CISA KEV list and no public proof-of-concept is referenced, so this is best treated as a routine browser-hardening fix rather than an emergency. No EPSS score was provided in the input, so probabilistic exploitation likelihood could not be factored in - this is a data gap, not a signal of safety. The one caveat: Mozilla's advisories (MFSA2026-106/108) are terse and the Bugzilla entry (bug 2068372) is almost certainly access-restricted as is typical for security bugs, so the precise nature of the disclosed information is not independently verifiable from the provided data.

An attacker hosts or compromises a web page and lures a Firefox user into visiting it (the UI:R requirement). When the browser processes the malicious content through the affected Networking component, a limited amount of information the user's browser should have kept private is leaked back to the attacker. No proof-of-concept or active exploitation is referenced, and the low attack complexity means a successful lure reliably triggers the flaw.