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CVE Record

CVE-2026-42897: Microsoft Exchange Server Spoofing Vulnerability

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.

HighCVSS 8.1Known exploitedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This high-severity Microsoft Exchange Server flaw lets an unauthenticated remote attacker use cross-site scripting to spoof trusted content. Successful exploitation requires user interaction but may compromise sensitive information and content integrity. CISA’s Known Exploited Vulnerabilities status confirms exploitation in the wild, making exposed affected servers an urgent business risk.

Executive priority

Treat this as an urgent remediation item because affected Exchange systems may handle sensitive communications and CISA reports known exploitation. Prioritize internet-accessible instances, confirm ownership and patch status promptly, and require documented exceptions for delayed remediation. The available evidence supports urgency but not a critical rating because user interaction is required and no availability impact is stated.

Technical view

CVE-2026-42897 is CWE-79: improper neutralization of input during web-page generation. It is remotely reachable without authentication, has low attack complexity, and requires victim interaction. CVSS 3.1 is 8.1, with high confidentiality and integrity impact but no stated availability impact. The supplied evidence does not describe the vulnerable input, attack path, or patch version.

Likely exposure

Potentially exposed deployments include Exchange Server 2016 CU23, Exchange Server 2019 CU14 or CU15, and Exchange Server Subscription Edition RTM as listed. Internet-accessible affected services likely deserve the fastest review. The bundle does not establish whether every installation is reachable or exploitable under all configurations.

Exploitation context

CISA KEV status supports active exploitation in the wild. The attacker can be unauthorized and operate over a network, but exploitation requires user interaction. Public evidence supplied here does not identify threat actors, campaign scale, exploitation frequency, affected interface, or observed indicators of compromise.

Researcher notes

The supplied vector is 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. Evidence identifies XSS resulting in spoofing but omits the sink, source, endpoint, prerequisites, indicators, and precise fixed builds. Researchers should use Microsoft’s advisory for patch-level details and avoid assuming a specific Exchange interface or exploit chain.

Mitigation direction

  • Inventory deployments of the listed Exchange Server releases immediately.
  • Review Microsoft’s advisory for the applicable security update and installation requirements.
  • Apply Microsoft’s prescribed update using established emergency change procedures.
  • Restrict unnecessary network exposure while remediation is pending.
  • Preserve relevant security logs for investigation of potentially exposed systems.

Validation and detection

  • Confirm each Exchange server’s edition, cumulative update, build, and patch status.
  • Compare installed updates with Microsoft’s CVE-2026-42897 advisory.
  • Verify affected services are not unnecessarily internet-accessible.
  • Review available logs and alerts for suspicious web activity around Exchange.
  • Reassess exposure after remediation and document any systems awaiting updates.
Prepared
Confidence
high
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-79: User-session and phishing behavior lookup

Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-42897 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
8.1 (3.1)
Known Exploited
Yes
Published

Vector: 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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
5Timeline events
1ADP providers
3Source links

CISA KEV status

Status
Known exploited
Source
CISA-ADP
Date added
KEV reference

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: activeAutomatable: noTechnical Impact: total

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.1CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C2.85.2microsoft

Vulnerability scoring details

Base CVSS 3.1 score

8.1High
CVSS 3.1 vector shape for CVE-2026-42897Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: 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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. Added to KEVCISA-ADP

    CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.

  4. ADP timelineCISA-ADP

    CVE-2026-42897 added to CISA KEV

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvcother:kev
  • 2026-05-15T00:00:00.000Z: CVE-2026-42897 added to CISA KEV

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 2315.01.0.0Listed
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 1415.02.0.0Listed
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 1515.02.0.0Listed
MicrosoftMicrosoft Exchange Server Subscription Edition RTM15.02.0.0Listed
Weakness

CWE details

CWE-79

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.