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CVE-2021-32749— Possible RCE vulnerability in mailing action using mailutils (mail-whois)

Quick assessment

Affected
fail2ban fail2ban
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

fail2ban是一个应用软件。禁止导致多个身份验证错误的主机。 fail2ban存在代码注入漏洞，该漏洞可能导致远程代码执行。要利用该漏洞，攻击者需要通过 MITM 攻击或接管 whois 服务器将恶意字符插入到 whois 服务器发送的响应中。以下产品和版本受到影响：0.9.7 及更早版本、0.10.0到0.10.6版本、0.11.0到0.11.2版本。

CVSS 6.1 · Medium EPSS 3.62% · P89

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2021-32749

Vulnerability Information
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Vulnerability Title
Possible RCE vulnerability in mailing action using mailutils (mail-whois)
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
OS命令中使用的特殊元素转义处理不恰当(OS命令注入)
Source: CVE Program / CVE List V5
Vulnerability Title
fail2ban 代码注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
fail2ban是一个应用软件。禁止导致多个身份验证错误的主机。 fail2ban存在代码注入漏洞，该漏洞可能导致远程代码执行。要利用该漏洞，攻击者需要通过 MITM 攻击或接管 whois 服务器将恶意字符插入到 whois 服务器发送的响应中。以下产品和版本受到影响：0.9.7 及更早版本、0.10.0到0.10.6版本、0.11.0到0.11.2版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
fail2ban fail2ban <= 0.9.7 -

II. Public POCs for CVE-2021-32749

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III. Intelligence Information for CVE-2021-32749

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Patches & Fixes for CVE-2021-32749 (2)

Vendor Advisories for CVE-2021-32749 (2)

Mailing List Discussions for CVE-2021-32749 (1)

IV. Related Vulnerabilities

Same product: fail2ban
Same vendor: fail2ban
Same weakness: CWE-78

V. Comments for CVE-2021-32749

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