CVE-2021-43890 Microsoft Windows AppX Installer Spoofing
Attackers can spoof AppX packages to execute malware via phishing, impacting Windows users, especially those with administrative rights.
- Exploited in the wild
- Since 15 Dec 2021
- 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-2021-43890?
CVE-2021-43890 is a high-severity vulnerability in Microsoft App Installer, published on 15 Dec 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
We have investigated reports of a spoofing vulnerability in AppX installer that affects Microsoft Windows. Microsoft is aware of attacks that attempt to exploit this vulnerability by using specially crafted packages that include the malware family known as Emotet/Trickbot/Bazaloader. An attacker could craft a malicious attachment to be used in phishing campaigns. The attacker would then have to convince the user to open the specially crafted attachment. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. Please see the Security Updates table for the link to the updated app. Alternatively you can download and install the Installer using the links provided in the FAQ section. Please see the Mitigations and Workaround sections for important information about steps you can take to protect your system from this vulnerability. December 27 2023 Update: In recent months, Microsoft Threat Intelligence has seen an increase in activity from threat actors leveraging social engineering and phishing techniques to target Windows OS users and utilizing the ms-appinstaller URI scheme. To address this increase in activity, we have updated the App Installer to disable the ms-appinstaller protocol by default and recommend other potential mitigations.
Which versions are affected by CVE-2021-43890?
It affects 1 product.
Products include Microsoft App Installer.
How do I fix CVE-2021-43890?
No fix has been published for CVE-2021-43890 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 29 Dec 2021.
Is CVE-2021-43890 being exploited?
Yes. Attackers have exploited CVE-2021-43890 in the wild since at least 15 Dec 2021, including in ransomware campaigns.
Other vulnerabilities in Microsoft App Installer
Sources
Also known as GHSA-hvcq-2mcq-rg5f.