CVE-2024-34083: STARTTLS unencrypted commands injection

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-18 · updated 2026-06-17
Weakness: CWE-349

Description

aiosmptd is a reimplementation of the Python stdlib smtpd.py based on asyncio. Prior to version 1.4.6, servers based on aiosmtpd accept extra unencrypted commands after STARTTLS, treating them as if they came from inside the encrypted connection. This could be exploited by a man-in-the-middle attack. Version 1.4.6 contains a patch for the issue.

Affected products

aio-libs aiosmtpd: before 1.4.6 — fixed in 1.4.6

How to fix

Upgrade to a fixed version: aio-libs aiosmtpd 1.4.6. Check the vendor advisory for mitigations.

References

https://github.com/aio-libs/aiosmtpd/commit/b3a4a2c6ecfd228856a20d637dc383541fcdbfda
https://github.com/aio-libs/aiosmtpd/security/advisories/GHSA-wgjv-9j3q-jhg8
https://nostarttls.secvuln.info
https://github.com/aio-libs/aiosmtpd/commit/b3a4a2c6ecfd228856a20d637dc383541fcdbfda
https://github.com/aio-libs/aiosmtpd/security/advisories/GHSA-wgjv-9j3q-jhg8
https://nostarttls.secvuln.info

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