CVE-2026-21851Public exploitNetwork attack vector

Arbitrary file write via unchecked archive extraction

Published Jan 7, 2026 · Updated Jan 7, 2026

Path traversal in MONAI 1.5.1 and earlier allows remote attackers to write files outside the bundle directory through a crafted ZIP. The _download_from_ngc_private() function in monai/bundle/scripts.py passes archive members to ZipFile.extractall() without verifying that resolved paths remain under the extraction root. Exploitation requires control of an NGC private repository and a victim configured to download it with source="ngc_private"; writes use the victim process's permissions.

CVSS severity5.3
Medium
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in MONAI 1.5.1 and earlier allows remote attackers to write files outside the bundle directory through a crafted ZIP. The _download_from_ngc_private() function in monai/bundle/scripts.py passes archive members to ZipFile.extractall() without verifying that resolved paths remain under the extraction root. Exploitation requires control of an NGC private repository and a victim configured to download it with source="ngc_private"; writes use the victim process's permissions.

The record

CVE
CVE-2026-21851
Published
Jan 7, 2026
Updated
Jan 7, 2026
Vendor
Project MONAI
Product
MONAI
Classifications
CWE-22, T1195.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 7, 2026Record 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=<= 1.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Project MONAI · MONAIversion=<= 1.5.1

Published CVSS scores

5.3GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A: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.

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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-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1195.002Compromise Software Supply Chain

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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