Critical Man-in-the-Middle Vulnerability in aiosmtpd Package
Summary
CVE-2024-34083: aiosmptd is a reimplementation of the Python stdlib smtpd.py based on asyncio. Affects python-aiosmtpd across 2 version ranges.
< 1.2.2-1+deb11u1
< b3a4a2c6ecfd228856a20d637dc383541fcdbfda
Fixed in 1.2.2-1+deb11u1. How to fix ↓
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Background
aiosmtpd is a reimplementation of the Python standard library's smtpd.py, designed to work with asyncio for asynchronous network programming. It allows developers to create SMTP servers that can handle email sending and receiving in a non-blocking manner. However, prior to version 1.4.6, aiosmtpd had a significant security flaw that allowed unencrypted commands to be accepted after a STARTTLS command, potentially exposing sensitive data to attackers.
Vulnerability Detail
The vulnerability, identified as CVE-2024-34083, arises from the handling of commands after the STARTTLS command in aiosmtpd versions prior to 1.4.6. When a server accepts extra unencrypted commands post-STARTTLS, it mistakenly treats them as if they originated from within an encrypted connection. This flaw can be exploited through a man-in-the-middle attack, where an attacker intercepts and manipulates the communication between the client and server, leading to potential data breaches and unauthorized access.
How To Fix
Minimum fixed version
1.2.2-1+deb11u1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade python-aiosmtpdTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary measure, if upgrading is not immediately feasible, consider disabling STARTTLS in your SMTP server configuration until the package can be updated. This will prevent the acceptance of unencrypted commands but may reduce the overall security of email transmission.
Conclusion
The aiosmtpd package has a critical vulnerability that can be exploited through man-in-the-middle attacks, allowing unauthorized access to sensitive data. It is crucial to upgrade to the patched versions to mitigate this risk. Users can also utilize Vulert to monitor and alert for such vulnerabilities in their software.
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FAQ
CVE-2024-34083 is a vulnerability in the aiosmtpd package that allows unencrypted commands to be accepted after a STARTTLS command, posing a risk of man-in-the-middle attacks.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
Exploitation of this vulnerability can lead to unauthorized access to sensitive data, as attackers can intercept and manipulate communications between the client and server.
Versions of aiosmtpd prior to 1.4.6 are affected by this vulnerability, with specific fixes available in versions 1.2.2-1+deb11u1, 1.4.3-1.1+deb12u1, and 1.4.6-1.
If an immediate upgrade is not possible, consider disabling STARTTLS in your SMTP server configuration as a temporary workaround.
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