CVE-2026-42897 (GCVE-0-2026-42897)

Vulnerability from cvelistv5 – Published: 2026-05-14 17:00 – Updated: 2026-08-10 15:14
VLAI CISA ENISA Previdian
Title
Microsoft Exchange Server Spoofing Vulnerability
Summary
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.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C
SSVC
Exploitation: active Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-14 00:00 UTC
CWE
  • CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
Impacted products
Date Public
2026-05-14 14:00
CISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: cbe424e5-4ff7-4307-a7a1-d4dd39db5c49

Vulnerability ID: CVE-2026-42897

Status: Confirmed

Status Updated: 2026-05-15 02:00 CEST

Exploited: Yes

Timestamps
First Seen: 2026-05-15
Asserted: 2026-05-15
Scope
Notes: Microsoft Exchange Server Cross-Site Scripting Vulnerability | Affected: Microsoft / Microsoft | Description: Microsoft Exchange Server contains a cross-site scripting vulnerability during web page generation in Outlook Web Access and when certain interaction conditions are met, arbitrary JavaScript can be executed in the browser context. | 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. | Due date: 2026-05-29 | Known ransomware campaign use (KEV): Unknown | Notes (KEV): https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-42897 ; https://learn.microsoft.com/en-us/exchange/plan-and-deploy/post-installation-tasks/security-best-practices/exchange-emergency-mitigation-service ; https://nvd.nist.gov/vuln/detail/CVE-2026-42897
Evidence

Type: Vendor Report

Signal: Successful Exploitation

Confidence: 80%

Source: cisa-kev

Details
Cwes CWE-79
Feed CISA Known Exploited Vulnerabilities Catalog
Product Microsoft
Due Date 2026-05-29
Date Added 2026-05-15
Vendorproject Microsoft
Vulnerabilityname Microsoft Exchange Server Cross-Site Scripting Vulnerability
Knownransomwarecampaignuse Unknown
References
Created: 2026-10-02 08:09 CEST | Updated: 2026-10-02 08:09 CEST
ENISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 9a15646b-1b7f-445b-992a-e4443be50f0b

Vulnerability ID: CVE-2026-42897

Status: Confirmed

Status Updated: 2026-08-18 02:00 CEST

Exploited: Yes

Timestamps
First Seen: 2026-08-18
Asserted: 2026-08-18
Scope
Notes: Affected: Microsoft / Microsoft Exchange Server | 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. | Patched since: 2026/05/14 | Exploitation type: unknown | CWEs: CWE-79 | Origin source: CERT.PL | Notes: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42897
Evidence

Type: Csirt Report

Signal: Successful Exploitation

Confidence: 75%

Source: enisa-cnw-kev

Details
Cwes CWE-79
Euvd EUVD-2026-30343
Notes https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42897
Catalog ENISA / EU CSIRTs Network (CNW) KEV JSON
Product Microsoft Exchange Server
Datereported 2026/08/18
Originsource CERT.PL
Patchedsince 2026/05/14
Vendorproject Microsoft
Exploitationtype unknown
Vulnerabilityname
Threatactorsexploiting
References
Created: 2026-10-02 08:52 CEST | Updated: 2026-10-02 08:52 CEST
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 8d7a07cd-3c45-434f-9828-6bdcee637c48

Vulnerability ID: CVE-2026-42897

Status: Confirmed

Status Updated: 2026-06-01 15:29 CEST

Exploited: Yes

Timestamps
First Seen: 2026-06-01
Asserted: 2026-06-01
Scope
Notes: Microsoft Exchange Server Spoofing Vulnerability | Affected: Microsoft / Microsoft Exchange Server 2016 Cumulative Update 23, Microsoft Exchange Server 2019 Cumulative Update 14, Microsoft Exchange Server 2019 Cumulative Update 15, Microsoft Exchange Server Subscription Edition RTM | CVSS: 8.1 (HIGH) | EPSS: 0.00519 | Used in malware: unknown | Listed 1 day ahead of CISA KEV | Not yet in CISA KEV: False
Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: previdian

Details
Feed Previdian (previdian.com)
Title Microsoft Exchange Server Spoofing Vulnerability
Cve Id CVE-2026-42897
Vendor Microsoft
Ghsa Id None
Product Microsoft Exchange Server 2016 Cumulative Update 23, Microsoft Exchange Server 2019 Cumulative Update 14, Microsoft Exchange Server 2019 Cumulative Update 15, Microsoft Exchange Server Subscription Edition RTM
Added Date 2026-06-01T13:29:03.497Z
Cvss Score 8.1
Epss Score 0.00519
Previous Ids
Cvss Severity HIGH
Virtual Patch False
Cvss Estimated False
Epss Percentile 0.42013
Used In Malware unknown
Vulnerability Id CVE-2026-42897
Ahead Of Cisa Kev 
{
  "count": 1,
  "unit": "day"
}
Not Yet In Cisa Kev False
References
Created: 2026-10-02 09:09 CEST | Updated: 2026-10-02 09:09 CEST
Show details on NVD website
To clipboard 

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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.