Mozilla Firefox EUVD-2026-78475

Exploitation requires that the victim use one of the affected Firefox builds (before 156, ESR 115.41, ESR 140.16, or 153.3) and that they load attacker-controlled web content that creates and drives a WebGL context through the CanvasWebGL component - WebGL is enabled by default, so no non-default configuration is needed and the delivered page must simply render the crafted graphics data. The CVSS vector shows PR:N, so per the supplied metrics no authentication or prior account is required; the decisive limiter is UI:R, meaning an attacker cannot trigger this without a user visiting the page (no email-borne, document-parsing, or server-side vector is described). Because the vulnerability is in the browser graphics stack, exploitation is constrained to the affected browser process hierarchy - the flaw is described as producing privilege escalation rather than a full sandbox-escape-plus-persistence chain, and SSVC notes the bug is not automatable, implying no worm-like campaign tooling exists. No evidence indicates that extensions, plug-ins, or specific GPU vendors are required preconditions, and no KEV or public POC is associated with this CVE.

The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H) describes a remotely reachable, low-complexity, unauthenticated flaw whose only gate is user interaction - a single visit to a malicious or compromised page in an affected Firefox build, so even a mid-sized municipal IT team in radom should treat this as urgent given the large number of browsers under management. Offset that by the softer signals: CISA's SSVC assessment records Exploitation: none and Automatable: no, the CVE is not in KEV, no public exploit code or proof-of-concept has been identified, and no EPSS score was supplied in the source data (a data gap worth noting, since a high-EPSS value would materially change prioritization). Technical Impact is rated total, and the CWE-120 buffer overflow class is historically the most reliable kind of primitive for turning memory corruption into code execution, so although weaponization is not yet observed, the barrier to a working exploit is not high for a skilled researcher - consistent with the browser vendor's decision to backport the fix to four separate release branches. The practical conclusion is a high-priority patch-but-not-emergency posture: no evidence of exploitation in the wild, but a wide, internet-exposed attack surface and a high-impact primitive if a POC appears.

An attacker hosts a page containing a WebGL shader or buffer payload designed to trigger the flawed boundary check in CanvasWebGL, then drives traffic to it via phishing, malvertising, or a compromised legitimate site. When a victim opens the page in an unpatched Firefox build, the out-of-bounds write corrupts graphics-process memory, and the attacker uses the resulting primitive to escalate privileges and run code in a more trusted context. No public exploit code is known at time of analysis, and exploitation depends entirely on the victim loading the crafted content (UI:R), which limits mass, drive-by automation.