# CVE-2023-45150: Inviting excessive long email addresses to a calendar event makes the Nextcloud server unresponsive

> Attackers can cause server unresponsiveness by inviting excessively long email addresses to calendar events, requiring an upgrade of the Nextcloud Calendar app.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Oct 2023
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-r936-8gwm-w452

## What is CVE-2023-45150?

CVE-2023-45150 is a medium-severity denial of service vulnerability in nextcloud security-advisories, published on 16 Oct 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Nextcloud calendar is a calendar app for the Nextcloud server platform. Due to missing precondition checks the server was trying to validate strings of any length as email addresses even when megabytes of data were provided, eventually making the server busy and unresponsive. It is recommended that the Nextcloud Calendar app is upgraded to 4.4.4. The only workaround for users unable to upgrade is to disable the calendar app.

Weakness: CWE-354 (Improper Validation of Integrity Check Value), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2023-45150?

It affects 1 product.


Products: Nextcloud Calendar.

## How do I fix CVE-2023-45150?

No fix has been published for CVE-2023-45150 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-45150 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-45150 exists.

## Other vulnerabilities in nextcloud security-advisories

- [CVE-2025-66550](https://insights.sbomify.com/CVE-2025-66550/): Nextcloud Calendar attachments of local files are offered to downloaded (medium 5.7)
- [CVE-2022-24838](https://insights.sbomify.com/CVE-2022-24838/): Command Injection in Appointment Emails for Nextcloud Calendar (medium 5.3)
- [CVE-2025-66511](https://insights.sbomify.com/CVE-2025-66511/): Nextcloud Calendar app used predictable proposal participant tokens (medium 4.8)
- [CVE-2018-3763](https://insights.sbomify.com/CVE-2018-3763/): Cross-site scripting in Nextcloud Calendar application (medium 4.8)
- [CVE-2024-37316](https://insights.sbomify.com/CVE-2024-37316/): Nextcloud Calendar's event create can create attachments that link to other websites (medium 4.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-45150 and fix it if it is affected.

What it is: CVE-2023-45150 is a medium-severity denial of service vulnerability in nextcloud security-advisories, published on 16 Oct 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-45150 exists.

Affected product: nextcloud security-advisories. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2023-45150/ (Markdown: https://insights.sbomify.com/CVE-2023-45150/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-45150
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-45150
- OSV: https://osv.dev/vulnerability/CVE-2023-45150

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-45150/
Summaries are generated and may contain mistakes; the official description above is the record.