Overview
CVE-2025-45311 identifies a critical vulnerability found in fail2ban-client version 0.11.2. This security flaw stems from insecure permissions handling, which allows attackers with limited sudo privileges to execute arbitrary operations as the root user. This escalation of privilege could lead to complete system compromise.
Published on 2025-11-26T16:15:47.663, this vulnerability highlights the importance of proper permission management and regular security audits, even within widely-used security tools.
Technical Details
The vulnerability resides within how fail2ban-client handles permissions when invoked with sudo. Specifically, the client does not adequately validate the user context under which it’s operating, leading to a scenario where a user with restricted sudo access can leverage the fail2ban-client binary to bypass those restrictions.
The precise mechanism of exploitation involves manipulating the command-line arguments or configuration files accessed by fail2ban-client. By crafting specific payloads, a user can force the client to perform actions it would normally be prevented from doing, ultimately executing commands with root privileges.
CVSS Analysis
Currently, both the Severity and CVSS score are listed as N/A. However, given the potential for complete system compromise, it is highly likely that a CVSS score will be assigned and will be classified as HIGH or CRITICAL once further analysis is completed. The lack of a CVSS score at this time does *not* diminish the seriousness of the vulnerability. Monitor official channels for updates on the CVSS score.
Possible Impact
The impact of CVE-2025-45311 is significant. Successful exploitation allows an attacker with limited sudo privileges to:
- Gain full root access to the affected system.
- Install malware or backdoors.
- Modify system configurations.
- Steal sensitive data.
- Disrupt system services.
This vulnerability poses a severe threat to systems running vulnerable versions of fail2ban-client, particularly those in shared hosting environments or where user access is strictly controlled.
Mitigation and Patch Steps
The primary mitigation strategy is to upgrade to a patched version of fail2ban. Check the official Fail2ban website for announcements regarding the patch and update instructions. Until a patch is available, consider the following temporary mitigations:
- Restrict
sudoaccess: Carefully review and restrictsudoprivileges granted to users, ensuring they only have access to the minimum necessary commands. - Monitor system logs: Actively monitor system logs for suspicious activity related to
fail2ban-client.
Apply the official patch as soon as it becomes available. The vendor will likely release updated packages through their official repositories.
References
Gist: R-Security Analysis of CVE-2025-45311
Packet Storm Security: fail2ban-client Root Privilege Escalation
