Path Traversal in onnx (CVE-2026-49114)
Summary
Path traversal in onnx (CVE-2026-49114). Data can be tampered with by attackers. Exploitable via save_external_data. Mitigation: upgrade to 1.21.0 or later.
Original description
The description as published by the source.
Summary
The save_external_data method seems to include multiple issues introducing a local TOCTOU vulnerability, an arbitrary file read/write on any system. It potentially includes a path validation bypass on Windows systems.
Regarding the TOCTOU, an attacker seems to be able to overwrite victim's files via symlink following under the same privilege scope.
The mentioned function can be found here: https://github.com/onnx/onnx/blob/main/onnx/external_data_helper.py#L188
Details
Toctou
The vulnerable code pattern:
# CHECK - Is this a file?
if not os.path.isfile(external_data_file_path):
# Line 228-229: USE #1 - Create if it doesn't exist
with open(external_data_file_path, "ab"):
pass
# Open for writing
with open(external_data_file_path, "r+b") as data_file:
# Lines 233-243: Write tensor data
data_file.seek(0, 2)
if info.offset is not None:
file_size = data_file.tell()
if info.offset > file_size:
data_file.write(b"\0" * (info.offset - file_size))
data_file.seek(info.offset)
offset = data_file.tell()
data_file.write(tensor.raw_data)
There is a time gap between os.path.isfile and open with no atomic file creation flags (e.g. O_EXCEL | O_CREAT) allowing the attacker to create a symlink that is being followed (absence of O_NOFOLLOW), between these two calls. By combining these, the attack is possible as shown below in the…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-49114 has been found in onnx.
Attackers can target a specific entry point like save_external_data over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.1/10.
What to do: upgrade onnx to 1.21.0 or later.
If unsure, ask your IT team or search "onnx CVE-2026-49114" on the vendor's site.
CVE-2026-49114 (onnx) — CWE-22 / CVSS v3 7.1
Attack vector: local / unauthenticated
Attack surface: save_external_data / os.path.isfile / open / O_NOFOLLOW
Patched: 1.21.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Path traversal (CWE-22) exists in onnx. Attackers reach the vulnerable code path via save_external_data without authentication.
Check the vendor advisory for the affected versions of onnx. Attack surface: save_external_data / os.path.isfile / open / O_NOFOLLOW.
Severity: High (CVSS 7.1/10). Data can be tampered with by attackers.
Update to 1.21.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'onnx' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'onnx' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
onnxを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade onnx to 1.21.0ステージング環境で 1.21.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory cve.org
- exploit github.com
- web raw.githubusercontent.com
- web nvd.nist.gov
- web github.com
- web github.com