CVE-2025-4538Public exploitNetwork attack vector

Unauthenticated dangerous-file upload via extension denylist

Published May 11, 2025 · Updated May 12, 2025

Unrestricted file upload in kekingcn kkFileView 4.4.0 allows remote attackers to write dangerous files through /fileUpload. The endpoint accepts any nonempty extension except three denylisted values, then streams the supplied bytes under the client-controlled name into the demo directory. The route has no authentication check and uploading is enabled by default; this permits persistent file writes, but server-side execution is not demonstrated.

CVSS severity9.8
Critical
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unrestricted file upload in kekingcn kkFileView 4.4.0 allows remote attackers to write dangerous files through /fileUpload. The endpoint accepts any nonempty extension except three denylisted values, then streams the supplied bytes under the client-controlled name into the demo directory. The route has no authentication check and uploading is enabled by default; this permits persistent file writes, but server-side execution is not demonstrated.

The record

CVE
CVE-2025-4538
Published
May 11, 2025
Updated
May 12, 2025
Vendor
kekingcn
Product
kkFileView
Classifications
CWE-434, CWE-284, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 11, 2025CVE publishedPublication date reported by the CVE source.
  2. May 12, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

kekingcn · kkFileViewversion=4.4.0

Published CVSS scores

6.3VulDB CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
6.5VulDB CNAAV:N/AC:L/Au:S/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.3VulDB CNACVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
CWE-284Improper Access Control
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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