Detections
Analytics

Echo: aiosmtplib: security update to 5.1.2

medium Tenable Self-Hosted Container Security Plugin ID 461053

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

 - aiosmtplib is an asynchronous SMTP client for use with asyncio. Prior to 5.1.2, SMTPProtocol.start_tls in
 src/aiosmtplib/protocol.py consumes the server's 220 response and starts the TLS handshake without
 clearing SMTPProtocol._buffer. An active network attacker can place attacker-chosen SMTP response lines
 after the plaintext 220 response in the same network segment. The method then calls loop.start_tls; those
 bytes survive the transport upgrade and are parsed as the first response from inside the TLS session,
 desynchronizing subsequent SMTP command and response pairs. Connections using start_tls=True or
 opportunistic STARTTLS are affected, while connections using use_tls=True are not. This issue is fixed in
 version 5.1.2. (CVE-2026-55558)

Solution

Update the aiosmtplib library and its related packages to version 5.1.2 or later.

See Also

https://advisory.echohq.com/cve/CVE-2026-55558

Plugin Details

Severity: Medium

ID: 461053

Version: Revision 1.1

Type: Local

Published: 10/2/2026

Updated: 10/3/2026

Supported Sensors: Tenable Cloud Security, Tenable Self-Hosted Container Security

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.66

CVSS v2

Risk Factor: Medium

Base Score: 5.4

Temporal Score: 4

Vector: CVSS2#AV:N/AC:H/Au:N/C:N/I:C/A:N

CVSS Score Source: CVE-2026-55558

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.2

Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Exploit Ease: No known exploits are available

Patch Publication Date: 8/29/2026

Vulnerability Publication Date: 8/20/2026

Reference Information

CVE: CVE-2026-55558