CVE-2024-27305 | SMTP smuggling in aiosmtpd

aiosmtpd is a reimplementation of the Python stdlib smtpd.py based on asyncio. aiosmtpd is vulnerable to inbound SMTP smuggling. SMTP smuggling is a novel vulnerability based on not so novel interpretation differences of the SMTP protocol. By exploiting SMTP smuggling, an attacker may send smuggle/spoof e-mails with fake sender addresses, allowing advanced phishing attacks. This issue is also existed in other SMTP software like Postfix. With the right SMTP server constellation, an attacker can send spoofed e-mails to inbound/receiving aiosmtpd instances. This issue has been addressed in version 1.4.5. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Published: 2024-03-12 Last update: 2025-01-22 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2024-27305 is rated Moderate Risk (46.8/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.73%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2024-27305

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-31 0.54% 0.73% +0.19%
2 2026-01-08 0.56% 0.54% -0.02%
3 2025-12-24 — 0.56% —

Full EPSS history (15 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2024-27305

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]

Weakness enumeration for CVE-2024-27305

GitHub Security Advisory for CVE-2024-27305

GHSA-pr2m-px7j-xg65 · Severity: medium · Ecosystem: pip — aiosmtpd vulnerable to SMTP smuggling

OS Trackers for CVE-2024-27305

vendor priority summary link
debian not yet assigned CVE-2024-27305 not yet assigned priority: Debian including 1 source packages (python-aiosmtpd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2024-27305
ubuntu medium CVE-2024-27305 medium priority: Ubuntu including 1 source packages (python-aiosmtpd), 9 status rows across 9 suites (bionic, focal, jammy, mantic, noble, oracular, plucky, questing, upstream): needs-triage 6, ignored 3. https://ubuntu.com/security/CVE-2024-27305

Affected software / configurations for CVE-2024-27305

Vendor Product Version Raw CPE
aio-libs aiosmtpd < 1.4.5 cpe:2.3:a:aio-libs:aiosmtpd:*:*:*:*:*:*:*:*

References for CVE-2024-27305

cvelogic Threat Intelligence