Microsoft Security Update Guide · Skype for Business
Skype for Business Remote Code Execution Vulnerability
Published
What does this mean?
- Remote Code Execution. An attacker can run their own code on the system remotely. This is the most serious type: it can lead to taking over the system.
- It can be exploited over the network (including from the internet if the service is reachable there), with an ordinary user account and without any user action.
- CVSS 8.8 out of 10: high. Microsoft rates it Important.
- No attacks reported; Microsoft expects exploitation to be less likely.
- What should you do? Install the security update for the version you run (or a later cumulative update):
- Skype for Business Server 2019 CU8: KB5131693
7.0.2046.583 - Skype for Business Server 2015 CU13: KB5132779
6.0.9319.886 - Skype for Business Server Subscription Edition CU1: KB5131692
7.0.2046.889
- Skype for Business Server 2019 CU8: KB5131693
Absolute path traversal in Skype for Business and Microsoft Lync allows an authorized attacker to execute code over a network.
Key facts
Released
13 okt 2026
Impact
Remote Code Execution
Max severity
Important
Weakness
CVSS 3.1
8.8 / 7.7 (base / temporal)
Vector string
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CPublicly disclosed
No
Exploited
No
Exploitability assessment
Exploitation Less Likely
Customer action required
Yes
Links
CVSS metrics
| Base score metrics | |
|---|---|
| Attack Vector | Network |
| Attack Complexity | Low |
| Privileges Required | Low |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity | High |
| Availability | High |
| Temporal score metrics | |
| Exploit Code Maturity | Unproven |
| Remediation Level | Official Fix |
| Report Confidence | Confirmed |
Affected products and updates
| Product | Update | Build |
|---|---|---|
| Skype for Business Server 2019 CU8 | KB5131693 | 7.0.2046.583 |
| Skype for Business Server 2015 CU13 | KB5132779 | 6.0.9319.886 |
| Skype for Business Server Subscription Edition CU1 | KB5131692 · Security Update | 7.0.2046.889 |
FAQ
- How could an attacker exploit this vulnerability?
- An authenticated attacker who holds a valid file token could send a specially crafted request containing a path traversal sequence to an affected Skype for Business Persistent Chat server. Successful exploitation could allow the attacker to execute code on the server. User interaction is not required.
Revisions
| Version | Date | Note |
|---|---|---|
| 1 | 13 okt 2026 | Information published. |
This is in the weekly digest for week 42: everything that changed in Microsoft 365 this week. →
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Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.
