Path Traversal in copier (CVE-2026-34730)
Summary
Path traversal in copier (CVE-2026-34730). Confidential information can be exposed externally. Exploitable via _external_data. Mitigation: upgrade to 9.14.1 or later.
Original description
The description as published by the source.
Copier is a library and CLI app for rendering project templates. Prior to version 9.14.1, Copier's _external_data feature allows a template to load YAML files using template-controlled paths. If untrusted templates are in scope, a malicious template can read attacker-chosen YAML-parseable local files that are accessible to the user running Copier and expose their contents in rendered output. This issue has been patched in version 9.14.1.
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-2026-34730 has been found in copier.
Attackers can target a specific entry point like _external_data over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 5.5/10.
What to do: upgrade copier to 9.14.1 or later.
If unsure, ask your IT team or search "copier CVE-2026-34730" on the vendor's site.
CVE-2026-34730 (copier) — CWE-22 / CVSS v3 5.5
Attack vector: local / unauthenticated
Attack surface: _external_data / ForbiddenPathError / yaml.safe_load
Patched: 9.14.1 — 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 copier. Attackers reach the vulnerable code path via _external_data without authentication.
Check the vendor advisory for the affected versions of copier. Attack surface: _external_data / ForbiddenPathError / yaml.safe_load.
Severity: Medium (CVSS 5.5/10). Confidential information can be exposed externally.
Update to 9.14.1.
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 'copier' . 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
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1Identify exposure identify
grep -r 'copier' . | 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
copier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 copier to 9.14.1ステージング環境で 9.14.1 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 github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- web github.com