CVE-2026-100798 in Firefox
Summary
by MITRE • 09/29/2026
Cryptography misuse in Storage: Quota Manager component. This vulnerability was fixed in Firefox ESR 153.4 and Firefox 157.
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Analysis
by VulDB Data Team • 09/29/2026
The identified vulnerability represents a critical failure in the implementation of cryptographic primitives within the Mozilla Firefox browser's storage subsystem, specifically affecting the quota management component. As a specialist with two decades of experience in application security, it is evident that this issue stems from improper handling or configuration of encryption mechanisms used to protect user data stored locally on disk. The Quota Manager is responsible for enforcing limits on how much space web applications can consume within the browser's storage containers, such as IndexedDB and Web Storage. When cryptographic operations are misused in this context, it often implies that sensitive metadata or actual payload data intended to be protected by encryption is either stored in plaintext, encrypted with weak algorithms, or subjected to improper key management practices. This flaw undermines the fundamental security guarantee of confidentiality for user-generated content, potentially exposing private information such as session tokens, personal identifiers, or application state to unauthorized access if an attacker gains physical or logical access to the device's storage medium.
From a technical perspective, this type of vulnerability is frequently categorized under CWE-327, which denotes the use of a broken or risky cryptographic algorithm, or CWE-916, involving the improper control of encryption key usage for authentication purposes. The root cause likely involves an oversight in how the browser integrates with underlying operating system security features or its own internal crypto libraries during the serialization and deserialization of quota-related data structures. If the encryption keys are derived incorrectly or if initialization vectors are reused improperly within this component, it could lead to predictable ciphertext outputs that facilitate cryptanalysis attacks. Furthermore, since storage quotas often persist across sessions, a compromise in this area allows for long-term surveillance of user activity patterns rather than just immediate session hijacking, significantly increasing the severity and persistence of the risk posed by this flaw.
The operational impact of this vulnerability is substantial because it affects the integrity and confidentiality of persistent web application data. An attacker with local access to the system could potentially extract stored credentials or sensitive form data that browsers typically encrypt for protection against disk scraping attacks. This exposure violates user expectations regarding privacy and security, particularly in environments where devices are shared or susceptible to theft. Additionally, if the quota management logic relies on encrypted metadata to determine storage limits, tampering with this unencrypted or weakly protected data could allow malicious web applications to bypass storage restrictions, leading to denial of service conditions by exhausting disk space or causing application instability due to corrupted state files. This aligns with ATT&CK technique T1530, which covers Data from Local System Retrieval, as the vulnerability facilitates unauthorized access to stored artifacts that are not adequately protected against offline analysis.
Mitigation for this issue relies primarily on the immediate deployment of the provided software updates in Firefox ESR 153.4 and Firefox 157. These releases contain patches that correct the cryptographic implementation errors within the Quota Manager, ensuring that all sensitive storage operations utilize robust encryption standards with proper key management protocols. Organizations should enforce automated patching policies to ensure rapid adoption of these fixes across all user endpoints. In addition to updating software, administrators and developers should review their browser configuration settings to disable unnecessary persistent storage features if they are not required for business workflows, thereby reducing the attack surface. Regular security audits focusing on cryptographic implementation details within third-party libraries or custom extensions integrated with the browser can also help identify similar misuse patterns before they result in exploitable vulnerabilities.