CVE-2025-10536 is a vulnerability identified in the Networking Cache component of Mozilla Firefox and Thunderbird, specifically affecting Firefox versions earlier than 143 and Firefox ESR versions earlier than 140.3, as well as corresponding Thunderbird versions. The vulnerability is classified as an information disclosure issue (CWE-200), where sensitive information stored in the browser's cache can be accessed by an attacker. The CVSS 3.1 base score is 6.2, reflecting a medium severity level, with the vector indicating local attack vector (AV:L), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), high confidentiality impact (C:H), and no impact on integrity or availability (I:N/A:N). This means an attacker with local access to the affected system can exploit the flaw without needing to authenticate or trick the user, potentially reading sensitive cached data such as browsing history, cookies, or cached web content. The vulnerability does not affect the integrity or availability of the system or data. No patches or exploit code links are currently provided, and no known exploits in the wild have been reported as of the publication date (September 16, 2025). The flaw likely arises from improper isolation or access controls within the caching mechanism of the networking stack, allowing unauthorized local access to cached data. Given the local attack vector, exploitation requires the attacker to have some form of access to the victim's machine, such as through a shared workstation, multi-user environment, or via malware that can read local files. This vulnerability underscores the importance of securing local access and promptly updating Mozilla products to versions 143 or ESR 140.3 and above, where the issue is presumably fixed.

For European organizations, the primary impact of CVE-2025-10536 is the potential unauthorized disclosure of sensitive information cached by Firefox or Thunderbird. This can include browsing history, session tokens, cookies, or other cached web data that may reveal confidential business information or user credentials. Organizations with shared workstations, public access terminals, or environments where multiple users have local access are particularly at risk. The confidentiality breach could facilitate further attacks such as social engineering, credential theft, or espionage. Since the vulnerability does not affect integrity or availability, direct disruption of services or data manipulation is unlikely. However, the exposure of sensitive data could lead to compliance issues under GDPR if personal data is leaked, resulting in legal and reputational consequences. The lack of required user interaction or privileges means that malware or insider threats with local access could exploit this vulnerability silently. European enterprises relying heavily on Firefox and Thunderbird for communication and browsing, especially in sectors like government, finance, and critical infrastructure, could face elevated risks if not patched promptly.

To mitigate CVE-2025-10536, European organizations should: 1) Immediately update all instances of Mozilla Firefox to version 143 or later and Thunderbird to version 140.3 or later, where the vulnerability is resolved. 2) Enforce strict local access controls on shared and multi-user systems to prevent unauthorized users from accessing cached data. 3) Implement endpoint security solutions that detect and prevent unauthorized local file access or suspicious processes that could exploit this vulnerability. 4) Educate users about the risks of leaving sessions open on shared devices and encourage logging out or locking devices when unattended. 5) Regularly audit and monitor local system access logs to detect potential exploitation attempts. 6) Consider deploying application sandboxing or containerization to isolate browser cache data per user. 7) Review and update organizational policies regarding device sharing and local privilege management to minimize exposure. 8) Stay informed on Mozilla security advisories for any patches or updates related to this vulnerability.