DEBIAN-CVE-2026-55558
- Source
- https://security-tracker.debian.org/tracker/CVE-2026-55558
- Import Source
- https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55558.json
- JSON Data
- https://api.osv.dev/v1/vulns/DEBIAN-CVE-2026-55558
- Upstream
- Published
- 2026-08-20T15:17:31Z
- Modified
- 2026-09-19T22:47:39Z
- Severity
-
- 5.9 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N CVSS Calculator
- Summary
- [none]
- Details
-
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.
- References
Affected packages
Debian:12 / aiosmtplib
Package
- Name
- aiosmtplib
- Purl
- pkg:deb/debian/aiosmtplib?arch=source&distro=bookworm
Affected ranges
- Type
- ECOSYSTEM
- Events
-
Introduced0 Unknown introduced version / All previous versions are affected
Debian:13 / aiosmtplib
Package
- Name
- aiosmtplib
- Purl
- pkg:deb/debian/aiosmtplib?arch=source&distro=trixie
Affected ranges
- Type
- ECOSYSTEM
- Events
-
Introduced0 Unknown introduced version / All previous versions are affected
Debian:14 / aiosmtplib
Package
- Name
- aiosmtplib
- Purl
- pkg:deb/debian/aiosmtplib?arch=source&distro=forky