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PuMuKIT EUVDEUVD-2026-110807

| CVE-2026-4337 HIGH
Unrestricted Upload of File with Dangerous Type (CWE-434)
2026-10-27 INCIBE GHSA-57jc-x74j-f4w4
8.8
CVSS 4.0 · Vendor: INCIBE
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Reach exposed PuMuKIT upload endpoint
  2. Exploit
    Send crafted unauthenticated upload request
  3. Execution
    Write dangerous-type file to writable path
  4. Impact
    Execute uploaded code or delete files

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V5 - File Handling File type validation, storage isolation
MITRE ATT&CK

2 techniques across 2 tactics: Command and Control, Persistence

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

No authentication, user interaction, or special privilege is required (PR:N/UI:N) - exploitation is remote and unauthenticated against a reachable PuMuKIT instance. The concrete prerequisites stated by the source are that the attacker can reach the upload functionality and that the web server user has write permission to the target path; the file is written to 'any path where the web server user has write permissions.' Realistic impact is bounded by that write-permission scope and by whether the chosen directory is web-accessible and allows the uploaded file type to be executed - code execution depends on those conditions, whereas file deletion/overwrite (integrity and availability damage) is achievable wherever write access exists. The exact HTTP trigger and endpoint are not described in the available sources.

Impact

The signals point to a genuinely dangerous but not yet actively-exploited flaw whose real-world urgency is tempered by the product's limited footprint. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) describes a network-reachable, low-complexity, unauthenticated bug requiring no user interaction - the most accessible profile possible - and the impact metrics (VI:H/VA:H with VC:L) reflect that an unrestricted upload can overwrite or destroy files and, if the file lands in an executable web path, lead to code execution, while confidentiality exposure is comparatively low. Against this, the exploitation-likelihood signals are either absent or neutral: no EPSS probability was provided, the CVE is not listed in CISA KEV, and no public exploit or PoC reference is present in the input, so there is no public exploit identified at time of analysis. The vuln.today decision label is 'this_week' - elevated but short of 'act_now' or 'emergency' - which is consistent with a high-severity, easily-triggerable flaw that lacks evidence of mass or targeted exploitation. SSVC-style technical impact is high (destructive/integrity), but automatability and real exploitation status are unconfirmed. Net: a real priority to patch for anyone running PuMuKIT, but the niche deployment base and the absence of KEV/EPSS/PoC evidence argue against treating it as an in-the-wild emergency. Note two data limits - no fixed version is published in the input, and the affected scope is recorded only vaguely as 'PuMuKIT current version'.

Exploit ScenarioDerived

An unauthenticated attacker sends a crafted HTTP upload request to an exposed PuMuKIT instance and writes a file of an attacker-chosen type into any directory where the web server user has write access. If that directory is web-accessible and the file is executable (e.g. a server-side script), the attacker can then request it to run code; alternatively they can overwrite or delete existing files to disrupt the service. No public exploit was identified in the available sources.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 28, 2026

Remote, unauthenticated attackers can upload files of any type to arbitrary writable paths in PuMuKIT and can also delete files, according to CVE-2026-4337. The impact can extend to code execution when an uploaded file is placed in a web-accessible directory that executes that file type; otherwise the exposure is integrity and availability damage within the web server user's write scope, and the exact triggering endpoint is not described in the available sources. No public exploit code or CISA KEV entry has been identified at time of analysis.

RemediationAI

No vendor-released patch with a specific fixed version is identified in the supplied data; monitor the INCIBE advisory (https://www.incibe.es/en/incibe-cert/notices/aviso/unrestricted-upload-file-pumukit-application) and NVD entry (https://nvd.nist.gov/vuln/detail/CVE-2026-4337) for an update. Until a fix is available, restrict or disable the affected upload functionality at a reverse proxy/WAF or require authentication in front of upload endpoints, which may break intended public or media-upload workflows; constrain the web server user's write permissions to only the directories required for uploads and mount other application paths read-only, which can interfere with normal file management; and configure the web server to disable execution of uploaded file types in upload directories, which may prevent legitimate served content from running if it relies on those handlers. Review upload directories for unexpected files and deletions as a detection measure.

Affected VersionsENISA

PuMuKIT current version

Affects your stack

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Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

CVE-2026-4337 is a CWE-434 unrestricted file upload in PuMuKIT, identified in the CPE data as pumukit:pumukit with a wildcard version (EUVD lists 'PuMuKIT current version'). The flaw is that the upload handler does not restrict the file type or the destination path before saving attacker-supplied content; the web server user's filesystem write permissions therefore define where files can be placed and deleted. Code execution is conditional: it requires the chosen path to be web-accessible and configured to execute the uploaded file type, whereas file deletion and unauthorized file placement are possible wherever that write access exists. The supplied sources do not describe the specific HTTP endpoint or request that triggers the upload.

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Severity by source

Vendor (INCIBE) PRIMARY 8.8 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:H/SC:L/SI:L/SA:L
vuln.today AI 9.4 CRITICAL

Unauthenticated network upload with no user interaction (AV:N/AC:L/PR:N/UI:N); arbitrary file write and deletion give high integrity and availability impact, limited confidentiality (C:L).

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (INCIBE).

CVSS VectorVendor: INCIBE

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
Low
Vulnerable system: Integrity
High
Vulnerable system: Availability
High
Subsequent system: Confidentiality
Low
Subsequent system: Integrity
Low
Subsequent system: Availability
Low

DescriptionCVE.org

Unrestricted Upload of File with Dangerous Type vulnerability in the PuMuKIT application allows a unauthenticated user to upload any type of file to the server, and to any path where the web server user has write permissions. This could also allow them to delete files.

Executive ViewAI

Why It Matters

CVE-2026-4337 is a high-severity vulnerability in PuMuKIT that allows unauthenticated attackers to upload and delete arbitrary files, potentially leading to code execution. This puts the platform's integrity and availability at risk, and leadership should prioritize remediation to prevent service disruption and data compromise.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations include restricting network access, disabling file uploads, enforcing strict file type validation, and deploying a WAF.

Threat Intelligence Overview

EPSS Score
0.3%
Top 74% exploitable
Prevalence
Low
niche open-source media/academic portal, limited enterprise footprint
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact
High

Priority Score

44
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +44
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Malicious file upload attacks exploit insufficient validation when web applications accept user-provided files.

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