CVE-2021-26421 Skype for Business and Lync Spoofing Vulnerability
Medium 6.5
Published
Updated
Check this codebase for CVE-2021-26421 and fix it if it is affected.
What it is: CVE-2021-26421 is a medium-severity vulnerability in Microsoft Lync Server 2013 CU10, published on 11 May 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-26421 in the wild and no public exploit code.
Affected product: Microsoft Lync Server 2013 CU10. 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-2021-26421/ (Markdown: https://insights.sbomify.com/CVE-2021-26421/index.md)
An attacker can spoof content in Skype for Business and Lync, potentially misleading users about the source of messages.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2021-26421?
CVE-2021-26421 is a medium-severity vulnerability in Microsoft Lync Server 2013 CU10, published on 11 May 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Skype for Business and Lync Spoofing Vulnerability
Which versions are affected by CVE-2021-26421?
It affects 2 products.
Products include Microsoft Lync Server, Microsoft Skype for Business Server.
How do I fix CVE-2021-26421?
No fix has been published for CVE-2021-26421 yet. Limit exposure of the affected software until one is available.
Is CVE-2021-26421 being exploited?
There is no known exploitation of CVE-2021-26421 in the wild and no public exploit code.
Other vulnerabilities in Microsoft Lync Server 2013 CU10
- CVE-2022-33633 Skype for Business and Lync Remote Code Execution Vulnerability
- CVE-2021-26422 Skype for Business and Lync Remote Code Execution Vulnerability
- CVE-2022-26911 Skype for Business Information Disclosure Vulnerability
- CVE-2021-24073 Skype for Business and Lync Spoofing Vulnerability
- CVE-2021-24099 Skype for Business and Lync Denial of Service Vulnerability
Sources
Also known as GHSA-w6mv-8x3w-r7w5.