# CVE-2017-11786: Auth bypass in Skype for Business

> Attackers can steal reusable authentication hashes to hijack accounts and escalate privileges in Skype for Business.

- **Severity:** High 8.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 13 Oct 2017
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-2xjh-35wj-vw46

## What is CVE-2017-11786?

CVE-2017-11786 is a high-severity authentication bypass vulnerability in Microsoft Corporation Skype for Business, published on 13 Oct 2017. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Skype for Business in Microsoft Lync 2013 SP1 and Skype for Business 2016 allows an attacker to steal an authentication hash that can be reused elsewhere, due to how Skype for Business handles authentication requests, aka "Skype for Business Elevation of Privilege Vulnerability."

Weakness: CWE-294 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2017-11786?

It affects 2 products.


Products: Microsoft Lync, Microsoft Skype for Business.

## How do I fix CVE-2017-11786?

No fix has been published for CVE-2017-11786 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-11786 being exploited?

There is no known exploitation of CVE-2017-11786 in the wild and no public exploit code.

## Other vulnerabilities in Microsoft Corporation Skype for Business

- [CVE-2020-1025](https://insights.sbomify.com/CVE-2020-1025/): Microsoft Office Elevation of Privilege Vulnerability (critical 9.8)
- [CVE-2013-1302](https://insights.sbomify.com/CVE-2013-1302/): Use after free in n/a (critical 9.3)
- [CVE-2012-1849](https://insights.sbomify.com/CVE-2012-1849/): Path traversal in n/a (critical 9.3)
- [CVE-2018-8311](https://insights.sbomify.com/CVE-2018-8311/): Code injection in Microsoft Lync (high 8.8)
- [CVE-2017-0283](https://insights.sbomify.com/CVE-2017-0283/): Memory corruption in Uniscribe (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-11786 and fix it if it is affected.

What it is: CVE-2017-11786 is a high-severity authentication bypass vulnerability in Microsoft Corporation Skype for Business, published on 13 Oct 2017. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2017-11786 in the wild and no public exploit code.

Affected product: Microsoft Corporation Skype for Business. 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-2017-11786/ (Markdown: https://insights.sbomify.com/CVE-2017-11786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-11786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-11786
- OSV: https://osv.dev/vulnerability/CVE-2017-11786

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From sbomify Insights: https://insights.sbomify.com/CVE-2017-11786/
Summaries are generated and may contain mistakes; the official description above is the record.