Arbitrary file read via followed external-data symlink
Published Apr 1, 2026 · Updated Apr 1, 2026
Path traversal in ONNX before 1.21.0 allows remote attackers to read arbitrary host files through external model data. In onnx/checker.cc, std::filesystem::is_regular_file follows a supplied external-data symlink and treats its target as a permitted regular file. Exploitation requires the targeted process to load an attacker-supplied model and linked data, exposing files readable by that process.
Summary
What happened
Path traversal in ONNX before 1.21.0 allows remote attackers to read arbitrary host files through external model data. In onnx/checker.cc, std::filesystem::is_regular_file follows a supplied external-data symlink and treats its target as a permitted regular file. Exploitation requires the targeted process to load an attacker-supplied model and linked data, exposing files readable by that process.
The record
- CVE
- CVE-2026-27489
- Published
- Apr 1, 2026
- Updated
- Apr 1, 2026
- Vendor
- ONNX
- Product
- ONNX
- Classifications
- CWE-61, CWE-23, T1204.002, T1005
- Attack vector
- network
- 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
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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?
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
- Upstream external-data symlink proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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