CVE-2021-32749

What it is

fail2ban is a daemon to ban hosts that cause multiple authentication errors. In versions 0.9.7 and prior, 0.10.0 through 0.10.6, and 0.11.0 through 0.11.2, there is a vulnerability that leads to possible remote code execution in the mailing action mail-whois. Command `mail` from mailutils package used in mail actions like `mail-whois` can execute command if unescaped sequences (`\n~`) are available in "foreign" input (for instance in whois output). To exploit the vulnerability, an attacker would need to insert malicious characters into the response sent by the whois server, either via a MITM attack or by taking over a whois server. The issue is patched in versions 0.10.7 and 0.11.3. As a workaround, one may avoid the usage of action `mail-whois` or patch the vulnerability manually.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of data tampering.

Exploit odds

3.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-07-16 18:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:53 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.4% in the next 30 days (EPSS).
• Severity: 6.1 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-07-16 18:15 UTC

Last modified

2026-06-17 03:53 UTC

Exploit probability

3.4% · EPSS, next 30 days

Weakness

CWE-78 · OS command injection

Record status

Modified

Affected

• fail2ban ≤ 0.9.7
• fail2ban < 0.10.7
• fail2ban < 0.11.3
• Fedoraproject Fedora 34
• Fedoraproject Fedora 35

Attack profile CVSS 3.1 · 6.1

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

Required

Scope

Changed

Confidentiality

None

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-32749.md and follow it. Check whether this project is affected by CVE-2021-32749. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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