CVE-2025-4084 is a vulnerability identified in the "copy as cURL" feature of Mozilla Firefox ESR on Windows platforms. This feature allows users to copy HTTP requests as cURL commands for debugging or replication purposes. The vulnerability stems from insufficient escaping of special characters within the copied command string, classified under CWE-116 (Improper Encoding or Escaping of Output). An attacker can craft a malicious web page or content that, when a user invokes the "copy as cURL" command, results in a command string that includes malicious payloads. If the user subsequently executes this command in a command-line environment, it can lead to local code execution on the user's machine. The vulnerability affects Firefox ESR versions prior to 128.10 and Thunderbird versions prior to 128.10 on Windows only; other Firefox versions and platforms are unaffected. The CVSS v3.1 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 privileges and user interaction, and impacts confidentiality but not integrity or availability. No known exploits are currently in the wild. The vulnerability requires the user to be tricked into using the "copy as cURL" feature and then executing the resulting command, making social engineering a key component of exploitation. This vulnerability highlights the risk of command injection through insufficient sanitization in developer tools features.

For European organizations, the primary impact of CVE-2025-4084 is the potential for local code execution on Windows systems running vulnerable versions of Firefox ESR or Thunderbird. This could allow attackers to execute arbitrary commands with the privileges of the user, potentially leading to data theft, installation of malware, or lateral movement within networks. Confidentiality is at risk due to possible exposure of sensitive data through executed commands, though integrity and availability impacts are limited. The requirement for user interaction and local privileges reduces the likelihood of widespread automated exploitation but increases the risk in environments where users frequently use developer tools or command-line utilities. Organizations in sectors such as government, finance, and critical infrastructure that rely on Firefox ESR and Thunderbird for secure communications and web access may face increased risk. Additionally, the vulnerability could be leveraged in targeted phishing or social engineering campaigns to compromise endpoints. The absence of known exploits in the wild suggests a window for proactive mitigation before active exploitation occurs.

1. Apply patches as soon as Mozilla releases updates for Firefox ESR and Thunderbird that address CVE-2025-4084. 2. Until patches are available, restrict or monitor the use of the "copy as cURL" feature, especially among users with elevated privileges or in sensitive roles. 3. Implement endpoint protection solutions that can detect and block suspicious command-line executions originating from user actions. 4. Educate users about the risks of executing copied commands from untrusted sources and encourage verification of any command before execution. 5. Employ application whitelisting to prevent unauthorized execution of commands or scripts. 6. Use group policies or configuration management to disable or limit developer tool features if feasible in high-risk environments. 7. Monitor logs for unusual command-line activity that could indicate exploitation attempts. 8. Incorporate this vulnerability into phishing awareness training to reduce the risk of social engineering exploitation.