# CVE-2019-11340: Matrix Sydent mishandles emails

> Attackers can bypass email domain registration restrictions in Matrix Sydent by exploiting email parsing flaws when specific options are enabled.

- **Severity:** Medium 5.9 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Apr 2019
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-q9h8-gpw5-c95c, PYSEC-2026-843

## What is CVE-2019-11340?

CVE-2019-11340 is a medium-severity authentication bypass vulnerability in n/a, published on 19 Apr 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2019-11340?

3 open source packages ship an affected version, including matrix-sydent. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `matrix-sydent` | PyPI | All versions | 1.0.2 |
| `matrix-sydent` | PyPI | All versions | 1.0.2 |
| `matrix-sydent` | PyPI | All versions | 1.0.2 |

Products: Matrix Sydent.

## How do I fix CVE-2019-11340?

Upgrade matrix-sydent to 1.0.2 or later.

## Is CVE-2019-11340 being exploited?

There is no known exploitation of CVE-2019-11340 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2023-38686](https://insights.sbomify.com/CVE-2023-38686/): Sydent does not verify email server certificates (critical 9.3)
- [CVE-2021-29431](https://insights.sbomify.com/CVE-2021-29431/): SSRF in Sydent due to missing validation of hostnames (high 7.7)
- [CVE-2021-29430](https://insights.sbomify.com/CVE-2021-29430/): Denial of service attack via memory exhaustion (high 7.5)
- [CVE-2019-11842](https://insights.sbomify.com/CVE-2019-11842/): matrix-sydent and matrix-synapse Use Cryptographically Weak PRNG (high 7.5)
- [CVE-2021-29432](https://insights.sbomify.com/CVE-2021-29432/): Malicious users could control the content of invitation emails (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-11340 and fix it if it is affected.

What it is: CVE-2019-11340 is a medium-severity authentication bypass vulnerability in n/a, published on 19 Apr 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2019-11340 in the wild and no public exploit code.

Affected packages and fixed versions:
- matrix-sydent (PyPI): affected all versions; fixed in 1.0.2
- matrix-sydent (PyPI): affected all versions; fixed in 1.0.2
- matrix-sydent (PyPI): affected all versions; fixed in 1.0.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2019-11340/ (Markdown: https://insights.sbomify.com/CVE-2019-11340/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-11340
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-11340
- OSV: https://osv.dev/vulnerability/CVE-2019-11340

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-11340/
Summaries are generated and may contain mistakes; the official description above is the record.