CVE-2026-45503: microsoft exchange_server Improper Authorization
CVSS: 8.1v3.1HighModified
Published 09-06-2026Last modified 24-09-2026
Vulnerability summary
CVE-2026-45503 is a high (CVSS 8.1) Improper Authorization vulnerability in microsoft exchange_server. EPSS estimates a 0.86% chance of exploitation in the next 30 days, higher than 58.1% of scored vulnerabilities.
CVSS score
8.1/10
010
High · v3.1 (CVE.org)EPSS score
0.86%
0%100%
Low · +0.42 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 09-06-2026PublishedVulnerability first disclosed.
- 24-09-2026Last modifiedVulnerability information updated.
Description
Improper authorization in Microsoft Exchange Server allows an authorized attacker to disclose information over a network.
CVSS metrics
2 scores · 2 sources · 1 versionHigh 8.1Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:CSources2 sources · 6.5–8.1
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:NDiffers
EPSS trend
Probability
0.86%
Chance of exploitation in the next 30 days
Percentile
58%
Versus all other CVEs
30-day change
+0.42 pp
From 0.45% on 21-09-2026
21-09-202621-10-2026
EPSS score0.86%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-285Improper AuthorizationThe product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
- CWE-918Server-Side Request Forgery (SSRF)The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
Affected systems
Microsoft6 products
- exchange_server2016:cumulative_update_23 | 2019:cumulative_update_14 | 2019:cumulative_update_15
- exchange_server_subscription_edition< 15.02.2562.043
- 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
