What’s Vulnerable › Vulnerabilities

CVE-2026-49114: ONNX symlink-following and path-traversal arbitrary file write

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-08-21 · updated 2026-10-15
• Weakness: CWE-22

Description

In ONNX before 1.21.0, the 'save_external_data' function builds the external-data file path from the model's external_data location field and opens it for writing without 'O_NOFOLLOW/O_EXCL', after a non-atomic 'os.path.isfile()' check. A local attacker with write access to the directory where a victim serializes external data can deterministically pre-plant a symlink that is being followed, causing the victim's write to append to any file the victim can write, e.g. ~/.ssh/authorized_keys, cron files, or application configs. Fixed in 1.21.0.

Affected products

• onnx: before 1.21.0 — fixed in 1.21.0

How to fix

Upgrade to a fixed version: onnx 1.21.0. Check the vendor advisory for mitigations.

References

• https://github.com/onnx/onnx/security/advisories/GHSA-q56x-g2fj-4rj6
• https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/IT/white/2026/va-26-233-01.json
• https://www.cve.org/CVERecord?id=CVE-2026-49114

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