CVE-2026-42897
MediumExploitedPublic exploitImproper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
Published May 15, 2026 · Updated Aug 10, 2026 · Also known as EUVD-2026-30343, GHSA-3c39-338m-m4vp
Key Facts
Patch immediately- CVE-2026-42897 is a medium-severity vulnerability (CVSS 6.1 v3.1) affecting Exchange Server (Microsoft), Exchange Server 2016 (Microsoft), Exchange Server 2019 (Microsoft) and 6 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since May 14, 2026. Public exploit code is available.
- EPSS estimates a 0.5% probability of exploitation in the next 30 days.
- Fixed versions are available, including Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.069, Microsoft Exchange Server 2016 Cumulative Update 23 publication, Microsoft Exchange Server 2019 Cumulative Update 14 15.02.1544.041.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
6.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS (30-day exploit likelihood)
0.5%
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2026-42897 brief as a PDF
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Description
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | May 15, 2026 | May 29, 2026 | Not reported |
| Industry KEV feed | May 14, 2026 | May 29, 2026 | Not reported |
| CIRCL KEV | May 15, 2026 | May 29, 2026 | Not reported |
| ENISA EUVD | May 15, 2026 | n/a | Not reported |
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Affected Products
53 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Exchange ServerMicrosoft | 2016, 2016-cumulative_update_1, 2016-cumulative_update_10, 2016-cumulative_update_11, 2016-cumulative_update_12, 2016-cumulative_update_13, 2016-cumulative_update_14, 2016-cumulative_update_15 | n/a |
| Exchange Server 2016Microsoft | See advisory | n/a |
| Exchange Server 2019Microsoft | See advisory | n/a |
| Exchange Server SeMicrosoft | See advisory | n/a |
| Exchange Server Subscription EditionMicrosoft | See advisory | 15.02.2562.043 |
Patched Releases
Microsoft Exchange Server 2016 Cumulative Update 23
15.01.2507.069, publication
Microsoft Exchange Server 2019 Cumulative Update 14
15.02.1544.041, publication
Microsoft Exchange Server 2019 Cumulative Update 15
15.02.1748.046, publication
Exchange Server Subscription Edition
15.02.2562.043
Microsoft Exchange Server Subscription Edition RTM
15.02.2562.043, publication
Timeline
Added to Industry KEV feed
May 14, 2026
Publicly disclosed
May 15, 2026
Added to CISA KEV
May 15, 2026
Added to CIRCL KEV
May 15, 2026
Added to ENISA EUVD
May 15, 2026
Last updated
Aug 10, 2026
Weakness Type
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
References
- advisoryhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41615
- advisoryMicrosoft Exchange Server Spoofing Vulnerability
- advisoryUSOM advisory
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
Affected: Exchange Server (Microsoft) versions 2016, 2016-cumulative_update_1, 2016-cumulative_update_10, 2016-cumulative_update_11, 2016-cumulative_update_12, 2016-cumulative_update_13, 2016-cumulative_update_14, 2016-cumulative_update_15; Exchange Server 2016 (Microsoft); Exchange Server 2019 (Microsoft), among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since May 14, 2026.
Yes. It was added on May 15, 2026 with a federal remediation due date of May 29, 2026.
Public exploit code is available.
Fixed versions are available, including Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.069, Microsoft Exchange Server 2016 Cumulative Update 23 publication, Microsoft Exchange Server 2019 Cumulative Update 14 15.02.1544.041.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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