# CVE-2019-1029: Skype for Business and Lync Server Denial of Service Vulnerability

> An attacker can cause Skype for Business servers to stop responding by initiating rapid calls via a dial-in link.

- **Severity:** Medium 5.9 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Jun 2019
- **Updated:** 20 May 2025
- **Also known as:** GHSA-6m2x-7chh-x75q

## What is CVE-2019-1029?

CVE-2019-1029 is a medium-severity denial of service vulnerability in Microsoft Lync Server 2010, published on 12 Jun 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A denial of service vulnerability exists in Skype for Business. An attacker who successfully exploited the vulnerability could cause Skype for Business to stop responding. Note that the denial of service would not allow an attacker to execute code or to elevate the attacker's user rights.
To exploit the vulnerability, an attacker needs to obtain a dial-in link for a vulnerable server and then initiates a series of calls within a short amount of time.
The update addresses the vulnerability by correcting the way that Skype for Business server handles objects in memory.

## Which versions are affected by CVE-2019-1029?

It affects 1 product.


Products: Microsoft Lync Server.

## How do I fix CVE-2019-1029?

No fix has been published for CVE-2019-1029 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-1029 being exploited?

There is no known exploitation of CVE-2019-1029 in the wild and no public exploit code.

## Other vulnerabilities in Microsoft Lync Server 2010

- [CVE-2022-33633](https://insights.sbomify.com/CVE-2022-33633/): Skype for Business and Lync Remote Code Execution Vulnerability (high 7.2)
- [CVE-2021-26422](https://insights.sbomify.com/CVE-2021-26422/): Skype for Business and Lync Remote Code Execution Vulnerability (high 7.2)
- [CVE-2022-26911](https://insights.sbomify.com/CVE-2022-26911/): Skype for Business Information Disclosure Vulnerability (medium 6.5)
- [CVE-2021-26421](https://insights.sbomify.com/CVE-2021-26421/): Skype for Business and Lync Spoofing Vulnerability (medium 6.5)
- [CVE-2021-24073](https://insights.sbomify.com/CVE-2021-24073/): Skype for Business and Lync Spoofing Vulnerability (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-1029 and fix it if it is affected.

What it is: CVE-2019-1029 is a medium-severity denial of service vulnerability in Microsoft Lync Server 2010, published on 12 Jun 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-2019-1029 in the wild and no public exploit code.

Affected product: Microsoft Lync Server 2010. 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-2019-1029/ (Markdown: https://insights.sbomify.com/CVE-2019-1029/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-1029
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-1029
- OSV: https://osv.dev/vulnerability/CVE-2019-1029

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-1029/
Summaries are generated and may contain mistakes; the official description above is the record.