CVE-2025-4084 is a vulnerability identified in the "copy as cURL" feature of Mozilla Firefox ESR versions prior to 128.10 (and Thunderbird prior to 128.10) specifically on Windows platforms. The root cause of this vulnerability is insufficient escaping of special characters when generating the cURL command string. This flaw allows an attacker to craft malicious input that, when a user invokes the "copy as cURL" command, could lead to local code execution on the user's Windows system. The vulnerability is classified under CWE-116, which relates to improper encoding or escaping of output, leading to injection issues. Exploitation requires the user to perform the "copy as cURL" action on a crafted web resource or content, which means user interaction is necessary. The attacker must have some level of access to trick the user into copying a malicious cURL command, but no prior elevated privileges are required. The CVSS 3.1 base score is 5.7 (medium severity), with vector AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N, indicating network attack vector, low attack complexity, requires low privileges, user interaction required, unchanged scope, high confidentiality impact, no integrity or availability impact. No known exploits are currently in the wild, and no patches are explicitly linked yet, but the issue affects only Windows versions of Firefox ESR and Thunderbird, leaving other platforms unaffected. This vulnerability could allow an attacker to execute arbitrary code locally, potentially leading to data exposure or further system compromise if leveraged effectively.

For European organizations, the primary impact of CVE-2025-4084 lies in the potential for local code execution on Windows endpoints running vulnerable versions of Firefox ESR or Thunderbird. Since Firefox ESR is commonly used in enterprise environments due to its extended support and stability, organizations relying on these versions may face risks of targeted attacks where users are socially engineered to use the "copy as cURL" feature on malicious content. Successful exploitation could lead to unauthorized disclosure of sensitive information (confidentiality impact) without directly affecting system integrity or availability. This could be particularly damaging in sectors handling sensitive personal data, such as finance, healthcare, and government agencies. Additionally, local code execution could serve as a foothold for further lateral movement or privilege escalation within corporate networks. However, the requirement for user interaction and low privileges reduces the likelihood of widespread automated exploitation. The impact is thus moderate but should not be underestimated in environments with high-value targets or strict data protection requirements under GDPR.

1. Immediate mitigation should focus on updating Firefox ESR and Thunderbird to versions 128.10 or later where the vulnerability is addressed. 2. Until patches are available or deployed, organizations should educate users about the risks of using the "copy as cURL" feature, especially when prompted by untrusted or suspicious websites or emails. 3. Implement endpoint protection solutions capable of detecting unusual command execution patterns that may arise from exploitation attempts involving cURL commands. 4. Restrict or monitor the use of developer or advanced browser features like "copy as cURL" through group policies or browser configuration management where feasible. 5. Employ application whitelisting to prevent unauthorized execution of commands or scripts that could be triggered by malicious cURL commands. 6. Conduct phishing awareness campaigns emphasizing the dangers of interacting with unexpected browser features or commands. 7. Monitor logs for anomalous local command executions or user activities that correlate with the use of the vulnerable feature. 8. For critical systems, consider isolating or limiting the use of Firefox ESR on Windows until patched versions are deployed.