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CVE-2026-42897· NVD / CVE Program· CNA microsoft

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.

MediumCVSS 6.1 · v3.1KEVWeaponized No fix recorded

Noroxi analysis

No Noroxi analysis for this record yet

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Published
May 14, 2026
Updated
Aug 10, 2026
EPSS
0.5% · 42th percentile▼ 71
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Report tools

JSON

Action score

54

Plan

Add it to your regular patch cycle.

CVSS
24 / 40 · 6.1 / 10
CISA KEV
30 / 30 · Listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
active
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.1
CNA · microsoft
8.1
2.0 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on May 15, 2026. That signals real attacks, not theory.

Remediation deadline for government agencies: May 29, 2026.

Affected systems

VendorProduct
microsoftexchange server
microsoftexchange server subscription edition

Using exchange server? Add it to your stack and be the first to know about CVEs like this one. (Email server)

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • microsoft exchange server2016
  • microsoft exchange server2019
  • microsoft exchange server subscription editionbefore 15.02.2562.043

Versions reported by the vendor

Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.

  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 23

    • 15.01.0.0 and later · before 15.01.2507.069affected

  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 14

    • 15.02.0.0 and later · before 15.02.1544.041affected

  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 15

    • 15.02.0.0 and later · before 15.02.1748.046affected

  • Microsoft Microsoft Exchange Server Subscription Edition RTM

    • 15.02.0.0 and later · before 15.02.2562.043affected

Same product

microsoft: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-34523Microsoft Exchange Server Elevation of Privilege VulnerabilityKEV
    96Now
  • CVE-2021-34473Microsoft Exchange Server Remote Code Execution VulnerabilityKEV
    96Now
  • CVE-2021-26855Microsoft Exchange Server Remote Code Execution VulnerabilityKEV
    96Now
  • CVE-2022-41040Microsoft Exchange Server Elevation of Privilege VulnerabilityKEV
    95Now
  • CVE-2020-0688A remote code execution vulnerability exists in Microsoft Exchange software when the software fails to properly handle objects in memory, akKEV
    95Now
  • CVE-2021-42321Microsoft Exchange Server Remote Code Execution VulnerabilityKEV
    93Now

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:52026-05-15

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoCsame day
  3. CISA KEVsame day
  4. TodaySep 30, 2026+139 d
EPSS, last 120 days-71% in 7 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-5500861 days apartMicrosoft Exchange Server Spoofing Vulnerability
    38Monitor
  • CVE-2026-4550026 days apartMicrosoft Exchange Server Spoofing Vulnerability
    24Monitor
  • CVE-2026-4763126 days apartMicrosoft Exchange Server Spoofing Vulnerability
    21Monitor
  • CVE-2026-6291489 days apartMicrosoft Exchange Server Spoofing Vulnerability
    21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

nvd-primary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records