Arbitrary file read via followed external-data symlink
Published Apr 1, 2026 · Updated Apr 1, 2026
Symlink traversal in ONNX before 1.21.0 allows local users to read files outside a model directory through crafted external data. The resolve_external_data_location function rejects absolute paths and parent components but accepts a symlink because is_regular_file follows its target; the Python loader then opens the returned path. Exploitation requires an attacker-supplied model and symlink to be placed together, followed by a user or application loading its external tensor data, exposing any file readable by that process.
Summary
What happened
Symlink traversal in ONNX before 1.21.0 allows local users to read files outside a model directory through crafted external data. The resolve_external_data_location function rejects absolute paths and parent components but accepts a symlink because is_regular_file follows its target; the Python loader then opens the returned path. Exploitation requires an attacker-supplied model and symlink to be placed together, followed by a user or application loading its external tensor data, exposing any file readable by that process.
The record
- CVE
- CVE-2026-34447
- Published
- Apr 1, 2026
- Updated
- Apr 1, 2026
- Vendor
- ONNX
- Product
- ONNX
- Classifications
- CWE-22, CWE-61, T1204.002, T1005
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 1, 2026CVE publishedPublication date reported by the CVE source.
- Apr 1, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.21.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- ONNX external-data symlink traversal proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo