CVE-2026-10702: Firefox JIT Compiler Miscompilation DoS Vulnerability

Technical summary

CVE-2026-10702 is a JIT miscompilation vulnerability in Mozilla Firefox's JavaScript engine. The flaw resides in the JIT compilation phase (CWE-733: Race Condition in Check-Use Pattern; CWE-843: Access of Resource Using Wrong Type) where the compiler generates incorrect machine code from JavaScript source, potentially leading to denial of service. The vulnerability requires user interaction—specifically, visiting a crafted webpage—but does not involve authentication or complex attack setup. The miscompiled code can trigger exceptions or undefined behavior that crashes the JavaScript context or renderer process.

Business impact

For organizations relying on Firefox for web access or development workflows, this vulnerability primarily affects business continuity through unplanned browser crashes. End users may lose unsaved work and experience frustration with browsing sessions. The risk is moderate: widespread Firefox deployments could see a measurable uptick in support tickets, but there is no data exfiltration or lateral movement risk. Enterprise environments with standardized Firefox configurations may limit exposure if users do not visit untrusted sites.

Affected systems

Mozilla Firefox is the sole affected product. The vulnerability impacts all Firefox builds and versions prior to 151.0.3. Users of Firefox ESR (Extended Support Release) branches should verify patch availability and release timelines with Mozilla. Other Gecko-based browsers or Firefox derivatives may require separate assessment depending on their inclusion of the affected JIT code path and version currency.

Exploitability

Exploitation is straightforward in terms of prerequisites: an attacker needs only to host a malicious webpage and trick or socially engineer a user into visiting it. No exploit code, zero-day tooling, or advanced techniques are required—the JIT miscompilation triggers on normal browser navigation. However, the impact is limited to denial of service; an attacker cannot escalate to code execution or data theft. The requirement for user interaction (clicking a link or visiting a site) and the moderate severity reflect the practical difficulty of mass exploitation compared to network-based worms.

Remediation

Firefox users should update to version 151.0.3 or later as soon as possible. Mozilla typically delivers updates through the browser's automatic update mechanism; users can also manually check for updates via Help > About Firefox. ESR users should consult Mozilla's security advisories to identify the corresponding patched ESR version. Organizations managing Firefox deployments should verify patch availability and test in staging before widespread rollout to avoid disruption.

Patch guidance

Update Firefox to version 151.0.3 or later. Verify the installed version by navigating to Help > About Firefox (on Windows/Linux) or Firefox > About Firefox (on macOS). The browser will automatically check for updates; if an update is available, you will be prompted to restart the browser to apply it. For unattended or managed deployments, consult Mozilla's documentation on automated Firefox updates or consider using Firefox for Enterprise with managed update policies. After patching, confirm the version string reflects 151.0.3 or higher.

Detection guidance

Organizations cannot reliably detect in-the-wild exploitation of this vulnerability through endpoint telemetry alone, as it manifests as a crash or hang indistinguishable from other JavaScript engine failures. Browser crash logs and JavaScript error telemetry may show anomalies, but attribution to this CVE is difficult without correlation to known malicious domains. The best detection strategy is proactive: deploy the patch and monitor patch compliance via asset management tools. Behavioral monitoring for unusual spike in Firefox process crashes could serve as a weak indicator if a campaign targets a specific user population.

Why prioritize this

This vulnerability merits prompt but not emergency patching. The CVSS 3.1 score of 4.3 (MEDIUM) reflects limited attack surface (requires user interaction) and impact scope (availability only, no confidentiality or integrity loss). It is not listed in CISA's Known Exploited Vulnerabilities catalog, suggesting active exploitation in the wild is not yet documented or is limited in scope. Prioritize patching high-value users (executives, developers, researchers) and public-facing systems within 30 days, with full deployment across the organization within 60 days as part of routine browser maintenance.

Risk score, explained

CVSS 3.1 score of 4.3 (MEDIUM) is justified by: Attack Vector Network (AV:N) reflects the web-based attack surface; Attack Complexity Low (AC:L) indicates no special conditions are needed to trigger miscompilation; Privileges Required None (PR:N) reflects the unauthenticated nature of visiting a webpage; User Interaction Required (UI:R) accounts for the need to visit a malicious site; Scope Unchanged (S:U) limits impact to the affected process; and Confidentiality/Integrity None (C:N/I:N) with Availability Low (A:L) reflects crashes without data leakage. The score appropriately captures that this is a nuisance-level DoS, not a critical system compromise.

Frequently asked questions