Fail2Ban - CVE-2025-45311

No further action required - until proven otherwise

Direct Answer: CVE-2025-45311 was assigned to fail2ban-client v0.11.2, but the fail2ban developers themselves have stated that it is not a valid vulnerability. The CVE claims insecure permissions could allow privilege escalation, but the project maintainers reviewed it and concluded that the described behavior is expected and intentional, not a security flaw.

🔎 What CVE-2025-45311 Says

• The CVE description states: “Insecure permissions in fail2ban-client v0.11.2 allows attackers with limited sudo privileges to perform arbitrary operations as root.”
• This implies that someone with partial sudo rights could exploit fail2ban-client to escalate privileges.

🛠 Fail2ban Project’s Response

• The fail2ban maintainers reviewed the CVE and closed the issue as incorrect.
• Their reasoning:
  • Fail2ban is designed to run as root (unless configured rootless). Actions like banning IPs via iptables/ipsets/nftables inherently require root privileges.
  • The alleged “exploit” is simply the system executing arbitrary shell commands that the administrator configured fail2ban to run when banning occurs. This is documented behavior in the manpage, not a flaw.
  • To exploit this, an attacker would already need root or sudo access, which makes the CVE claim of privilege escalation misleading.
  • The second claim (unsanitized variables) lacks proof-of-concept and only applies if administrators misconfigure fail2ban actions with unsafe shell commands.

⚖️ Practical Implications

• No new risk is introduced by CVE-2025-45311 if fail2ban is used as intended.
• The only real risk is misconfiguration: if administrators insert unsafe shell commands into fail2ban actions, those commands will run as root. But that’s a configuration error, not a software vulnerability.
• Fail2ban maintainers consider the CVE a “bad joke or failed prank”.

✅ Advice for You

• If you’re running fail2ban, you do not need to patch or disable it because of CVE-2025-45311.
• Just ensure:
  • Your fail2ban actions are configured with safe, intended commands.
  • You follow the documented guidance on root vs. rootless operation.
  • You restrict sudo access properly—since anyone with sudo can already run arbitrary commands as root, regardless of fail2ban.

Summary: CVE-2025-45311 does not represent a real vulnerability in fail2ban. It’s essentially a mischaracterization of expected behavior. As long as your configuration is sane, you’re safe.

Sources: NVD CVE-2025-45311 Fail2ban GitHub issue discussion CVE Details summary

#enoughsaid