CVE-2026-55009: microsoft exchange_server Deserialization of Untrusted Data
CVSS: 7.8v3.1HighAnalyzed
Published 14-07-2026Last modified 08-10-2026
Vulnerability summary
CVE-2026-55009 is a high (CVSS 7.8) Deserialization of Untrusted Data vulnerability in microsoft exchange_server. EPSS estimates a 2.51% chance of exploitation in the next 30 days, higher than 84.5% of scored vulnerabilities.
CVSS score
7.8/10
010
High · v3.1 (CVE.org)EPSS score
2.51%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 14-07-2026PublishedVulnerability first disclosed.
- 08-10-2026Last modifiedVulnerability information updated.
Description
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
CVSS metrics
2 scores · 2 sources · 1 versionHigh 7.8Preferred score · CVE.org (CNA)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CSourcesAll 2 agree
- NVDNIST7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
2.51%
Chance of exploitation in the next 30 days
Percentile
85%
Versus all other CVEs
30-day change
0.00 pp
From 2.51% on 20-09-2026
20-09-202620-10-2026
EPSS score2.51%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Microsoft6 products
- exchange_server2016:cumulative_update_23 | 2019:cumulative_update_14 | 2019:cumulative_update_15
- exchange_server_subscription_edition< 15.02.2562.045
- microsoft exchange server 2016 cumulative update 23≥ 15.01.0.0, < 15.01.2507.071
- microsoft exchange server 2019 cumulative update 14≥ 15.02.0.0, < 15.02.1544.043
- microsoft exchange server 2019 cumulative update 15≥ 15.02.0.0, < 15.02.1748.048
1 vendor · 6 products
