CVE-2026-118153: Microsoft Exchange Server Denial of Service Vulnerability
CVE-2026-118153 is a denial of service vulnerability in Microsoft Exchange Server, rated Important by Microsoft, with a CVSS 3.1 base score of 7.5 (High). An attacker can exploit it remotely over the network, without any privileges and without user interaction. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. The EPSS model estimates a 1.30% probability of exploitation activity in the next 30 days, higher than 71% of all scored vulnerabilities. Microsoft released the fix on 10 November 2026 in the November 2026 Patch Tuesday, delivered through 1 security update (KB5133453). It affects 1 product in 1 product family (Server Software).
Key facts
- CVE ID
- CVE-2026-118153
- Severity
- High CVSS 7.5
- Microsoft severity
- Important
- Impact
- Denial of Service
- Exploited in the wild
- No
- Publicly disclosed
- No
- Exploitation likelihood
- Less Likely
- Weakness
- CWE-407
- EPSS
- 1.30% (percentile 71%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- November 2026 Patch Tuesday
- Product families
- Server Software
CVSS score and vector
Microsoft scores CVE-2026-118153 at 7.5 (temporal 6.5) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | None |
| Integrity impact | None |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
Inefficient algorithmic complexity in Microsoft Exchange Server allows an unauthorized attacker to deny service over a network.
Affected products (1)
Server Software
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Microsoft Exchange Server Subscription Edition RTM | KB5133453 | Security Update | 15.02.2562.057 | Yes |
Security updates (1)
- KB5133453 (Security Update)
NIST NVD data
- NVD status
- Awaiting Analysis
- NVD CVSS
- 7.5 (HIGH)
- NVD weakness
- CWE-407
- Published to NVD
- NVD last modified
References
Acknowledgments
- XlabAI
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |