CVE-2025-10532 is a medium severity vulnerability affecting Mozilla Firefox versions prior to 143, Firefox ESR versions prior to 140.3, and Thunderbird versions prior to 143 and 140.3 respectively. The vulnerability arises from incorrect boundary conditions in the JavaScript Garbage Collection (GC) component. Specifically, this flaw is categorized under CWE-754, which relates to improper checks for unusual or exceptional conditions. In this context, the GC component, responsible for automatic memory management in JavaScript execution, fails to correctly handle boundary conditions, potentially leading to memory corruption or unexpected behavior during garbage collection cycles. The vulnerability has a CVSS v3.1 base score of 6.5, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), and impacts confidentiality and integrity (C:L/I:L) but not availability (A:N). This indicates that an attacker can exploit this vulnerability remotely without authentication or user interaction, potentially leading to partial disclosure or modification of information within the browser or Thunderbird environment. Although no known exploits are currently reported in the wild, the nature of the vulnerability suggests that exploitation could allow attackers to execute arbitrary code or manipulate memory, which could be leveraged for further attacks such as data theft or browser compromise. The lack of available patches at the time of publication emphasizes the need for prompt vendor updates once they become available.

For European organizations, this vulnerability poses a moderate risk primarily to users relying on affected versions of Firefox and Thunderbird, which are widely used across Europe for web browsing and email communication. Exploitation could lead to unauthorized access to sensitive information, including corporate emails or browsing data, potentially resulting in data breaches or espionage. Given the network-based attack vector and no requirement for user interaction, attackers could target employees remotely, increasing the risk of widespread compromise within organizations. The impact is particularly significant for sectors handling sensitive or regulated data, such as finance, healthcare, and government agencies, where confidentiality and integrity of information are paramount. Additionally, since Thunderbird is often used for email, exploitation could facilitate interception or manipulation of email content, undermining communication security. However, the absence of availability impact reduces the likelihood of service disruption. Overall, the vulnerability could be leveraged as part of a broader attack chain to gain foothold or escalate privileges within corporate networks.

European organizations should prioritize upgrading affected Mozilla products to the latest versions as soon as patches are released. Until patches are available, organizations can implement network-level protections such as restricting access to Firefox and Thunderbird update servers to prevent downgrade attacks and monitoring network traffic for anomalous activity indicative of exploitation attempts. Employing endpoint detection and response (EDR) tools to detect unusual memory behavior or process anomalies related to Firefox and Thunderbird can help identify exploitation attempts early. Additionally, enforcing strict browser security policies, including disabling or limiting JavaScript execution in untrusted contexts, can reduce the attack surface. Organizations should also conduct user awareness training to recognize suspicious network behavior and ensure that all software inventories are up to date to quickly identify vulnerable endpoints. Finally, leveraging application whitelisting and sandboxing techniques for browsers and email clients can contain potential exploitation impacts.