Security readout for executives and security teams
Plain-English summary
MONAI versions 1.5.1 and earlier have a Zip Slip path traversal flaw in a private NGC bundle download function. If a user downloads and extracts a malicious bundle through this path, files outside the intended directory could be overwritten. This is a medium-severity integrity risk, not currently listed as actively exploited.
Executive priority
Treat as a targeted remediation item for healthcare AI and imaging environments using MONAI. It is not an emergency based on current sources, but affected private bundle workflows should be fixed promptly because successful exploitation can alter files and undermine workflow integrity.
Technical view
The vulnerable `_download_from_ngc_private()` function uses Python `zipfile.ZipFile.extractall()` without path validation. Similar MONAI functions use `safe_extract_member()`. A crafted ZIP with traversal paths could write outside the target extraction directory. The advisory maps this to CWE-22 and CVSS 3.1 score 5.3: network, high complexity, no privileges, user interaction required, high integrity impact.
Likely exposure
Organizations using Project-MONAI MONAI up to and including 1.5.1 are potentially exposed, especially workflows that download private NGC bundles. Exposure depends on whether this specific private bundle download path is used and whether untrusted or compromised bundle archives can be processed.
Exploitation context
Sources do not report active exploitation, and it is not marked CISA KEV. Exploitation requires user interaction and a crafted archive processed through the affected function. The main business risk is unauthorized file overwrite on systems running MONAI workflows, potentially affecting model files, scripts, or configuration integrity.
Researcher notes
The key code issue is inconsistent use of safe extraction logic: the private NGC download path used `extractall()` while comparable functions used `safe_extract_member()`. Public sources identify the fixing commit but do not provide evidence of exploitation in the wild or broader product impact beyond MONAI <= 1.5.1.
Mitigation direction
- Identify MONAI installations and versions in affected environments.
- Prioritize systems using NGC private bundle downloads.
- Update to a vendor-fixed MONAI release when available.
- If no release is available, evaluate applying commit 4014c8475626f20f158921ae0cf98ed259ae4d59.
- Restrict bundle sources to trusted channels until remediated.
- Monitor Project-MONAI advisory updates for official remediation guidance.
Validation and detection
- Confirm installed MONAI version is greater than 1.5.1 or includes the fix commit.
- Review dependency manifests, containers, notebooks, and ML pipelines for MONAI usage.
- Check whether `_download_from_ngc_private()` is reachable in operational workflows.
- Inspect remediation by verifying path validation is used during ZIP extraction.
- Review recent bundle download activity for unexpected file changes outside extraction paths.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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-22: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. 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 lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-21851 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
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.
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N1.63.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/Project-MONAI/MONAI/security/advisories/GHSA-9rg3-9pvr-6p27CVE reference · x_refsource_CONFIRM
- https://github.com/Project-MONAI/MONAI/commit/4014c8475626f20f158921ae0cf98ed259ae4d59CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.