CVE-2026-124229Microsoft 365 Apps for Enterprise deserialization of untrusted data
CVE-2026-124229 is a deserialization of untrusted data in Microsoft 365 Apps for Enterprise, rated medium (6.6 on CVSS 3.1).
Why this priority: Medium severity, with no exploitation signal.
Published · Updated · NVD status: Undergoing Analysis
What it is
Serialized objects from outside are turned back into live objects, which a crafted payload can abuse to run code.
How it is reached
An attacker can exploit it with physical access to the device, without an account, but someone has to act first, such as opening a file or following a link.
What an attacker gains
A successful attack can read the data it protects, change data or behaviour and take it offline. In practice, this kind of flaw lets an attacker turn crafted data into code execution inside the receiving service.
Is it being exploited?
There is no public report of exploitation yet.
What to do
- No fixed version is listed for Microsoft 365 Apps for Enterprise itself; fixed versions for the other affected products are listed on this page.
- Warn the people who use it, and filter files and links on the way in.
Description from NVD
Deserialization of untrusted data in Microsoft Office Excel allows an unauthorized attacker to execute code with a physical attack.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- APIs, queues and caches that accept serialized objects. The flaw sits between a message producer and the service that deserializes it.
Trust boundaries in play
- Host boundary. The attacker needs a foothold on the machine first; the flaw turns a small foothold into a bigger one.
- People who open files and links. Mail, chat and browsers are the delivery path.
- Between a message producer and the service that deserializes it. An attacker who crosses it can turn crafted data into code execution inside the receiving service.
Questions to answer about your own systems
- Where does Microsoft 365 Apps for Enterprise run in your systems, and at which version?
- Which of those devices sit where outsiders can touch them?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.