CVE-2021-32749

fail2ban: fail2ban is a daemon to ban hosts that cause multiple authentication errors

CVE-2021-32749 is fixed in fail2ban on 1 platform, first by fail2ban 0.10.2-2ubuntu0.1~esm1, released July 16, 2021. It is not reported as exploited. Patch Radar priority: Routine.

Routine
CVSS
n/a
Medium
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0343
89th percentile

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.

Where it's fixed

ProductFixed inFixReleased
Linux
fail2ban · Ubuntu 18.04.6 LTS (bionic) 0.10.2-2ubuntu0.1~esm1 fail2ban 0.10.2-2ubuntu0.1~esm1 Jul 16, 2021
fail2ban · Ubuntu 20.04 LTS (focal) 0.11.1-1ubuntu0.1~esm1 fail2ban 0.11.1-1ubuntu0.1~esm1 Jul 16, 2021

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