Heap-based Buffer Overflow in Mozilla Firefox

Executive Summary

CVE-2026-15718 is a security vulnerability in Mozilla Firefox version 152.0.6. It involves an invalid pointer in the JavaScript: WebAssembly component. This flaw can be exploited by attackers, and public exploit code is available, though no active exploitation in the wild has been detected.

The vulnerability was reported by Christian Holler and is tracked under Bug 2045443. It was fixed in Firefox 152.0.6.

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Detection Guidance

Detection of CVE-2026-15718 on your network or system primarily involves verifying the installed version of Firefox. This vulnerability affects Firefox versions prior to 152.0.6.

• Check the Firefox version on a system by opening Firefox and navigating to 'Help' > 'About Firefox'. The version number will be displayed.
• On Linux systems, you can run the command: firefox --version or check the package manager, e.g., dpkg -l | grep firefox or rpm -qa | grep firefox.
• On Windows systems, you can check the installed version via 'Control Panel' > 'Programs and Features' or by running wmic product where name='Mozilla Firefox' get version in Command Prompt.

Since this vulnerability involves WebAssembly, monitoring for unusual WebAssembly-related activity or crashes in Firefox logs may indicate exploitation attempts, though this is not a definitive detection method.

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Impact Analysis

This vulnerability can impact you if you are using an affected version of Mozilla Firefox (prior to 152.0.6).

• An attacker could exploit this flaw to access sensitive information on your system, as indicated by the CVSS score (Confidentiality impact: Low).
• While no active exploitation has been detected, the availability of public exploit code increases the risk of potential attacks.

To mitigate the risk, you should update to Firefox 152.0.6 or later.

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Compliance Impact

The vulnerability CVE-2026-15718 involves an invalid pointer in the JavaScript: WebAssembly component of Firefox, which could lead to limited information disclosure (confidentiality impact rated as 'Low' in the CVSS vector).

Under regulations like GDPR, any unauthorized access to personal data, even if limited, may constitute a breach of confidentiality requirements. Organizations processing personal data using affected Firefox versions could face compliance risks if the vulnerability is exploited to access such data.

For HIPAA, if the vulnerability is exploited to access protected health information (PHI), it could result in a reportable breach. Covered entities and business associates must ensure systems handling PHI are patched or mitigated to avoid violations of the Security Rule.

While the CVSS score (4.3) indicates a moderate severity, the presence of public exploit code increases the urgency for organizations to apply the fix (Firefox 152.0.6) to maintain compliance with data protection standards.

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Mitigation Strategies

The immediate step to mitigate CVE-2026-15718 is to upgrade Firefox to version 152.0.6 or later, as the vulnerability was fixed in this release.

• Download and install the latest version of Firefox from the official Mozilla website: https://www.mozilla.org/firefox.
• If automatic updates are enabled, ensure Firefox is updated by restarting the browser and checking the version as described in the detection steps.
• For enterprise environments, deploy the updated version of Firefox across all systems using centralized management tools or scripts.

If upgrading is not immediately possible, consider disabling WebAssembly in Firefox as a temporary workaround, though this may impact functionality of websites relying on WebAssembly.

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