{ "document": { "category": "csaf_base", "csaf_version": "2.0", "distribution": { "tlp": { "label": "WHITE" } }, "lang": "en", "notes": [ { "category": "legal_disclaimer", "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings." } ], "publisher": { "category": "coordinator", "contact_details": "cert@ncsc.nl", "name": "National Cyber Security Centre", "namespace": "https://www.ncsc.nl/" }, "title": "CVE-2026-34726", "tracking": { "current_release_date": "2026-04-03T16:39:32.698702Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-34726", "initial_release_date": "2026-04-01T23:02:31.550130Z", "revision_history": [ { "date": "2026-04-01T23:02:31.550130Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)." }, { "date": "2026-04-01T23:02:40.366673Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-04-02T19:03:30.575149Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (1).| References created (3).| CWES updated (1)." }, { "date": "2026-04-02T19:03:36.906663Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-04-02T20:10:11.080519Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)." }, { "date": "2026-04-02T20:10:13.169626Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-04-03T15:31:07.658899Z", "number": "7", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-04-03T16:39:22.517143Z", "number": "8", "summary": "Unknown change." } ], "status": "interim", "version": "8" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/<9.14.1", "product": { "name": "vers:unknown/<9.14.1", "product_id": "CSAFPID-5985269" } } ], "category": "product_name", "name": "copier" } ], "category": "vendor", "name": "copier-org" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-34726", "cwe": { "id": "CWE-22", "name": "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')" }, "notes": [ { "category": "description", "text": "### Summary\n\nCopier's `_subdirectory` setting is documented as the subdirectory to use as the template root. However, the current implementation accepts parent-directory traversal such as `..` and uses it directly when selecting the template root.\n\nAs a result, a template can escape its own directory and make Copier render files from the parent directory without `--UNSAFE`.\n\n### Details\n\nThe relevant code path is:\n\n1. the template defines `_subdirectory`\n2. Copier renders that string\n3. `template_copy_root` returns `self.template.local_abspath / subdir`\n4. Copier walks that directory as the template root\n\nRelevant code:\n\n- \n- \n\nThe effective sink is:\n\n```python\nsubdir = self._render_string(self.template.subdirectory) or \"\"\nreturn self.template.local_abspath / subdir\n```\n\nThere is no check that the resulting path stays inside the template directory.\n\nThe documentation for `_subdirectory` describes it as:\n\n> Subdirectory to use as the template root when generating a project.\n\nand explains it as a way to separate template metadata from template source code:\n\n\n\nThat description fits values like `template` or `poetry`, but not `..`.\n\n### PoC\n\n#### PoC 1: `_subdirectory: ..` escapes to the parent directory\n\n```sh\nmkdir -p root/template dst\necho 'loot' > root/loot.txt\nprintf '%s\\n' '_subdirectory: ..' > root/template/copier.yml\n\ncopier copy --overwrite root/template dst\nfind dst -maxdepth 3 -type f | sort\ncat dst/loot.txt\n```\n\nExpected output includes:\n\n```text\ndst/loot.txt\ndst/template/copier.yml\nloot\n```\n\nThis shows Copier is rendering from `root/` rather than from `root/template/`.\n\n### Impact\n\nIf a user runs Copier on an untrusted template, that template can change the effective template root and make Copier render files from outside the intended template directory.\n\nPractical impact:\n\n- template-root escape via `..`\n- rendering of parent-directory files that were not meant to be part of the template\n- possible without `--UNSAFE`", "title": "github - https://api.github.com/advisories/GHSA-85v3-4m8g-hrh6" }, { "category": "description", "text": "Copier is a library and CLI app for rendering project templates. Prior to version 9.14.1, Copier's _subdirectory setting is documented as the subdirectory to use as the template root. However, the current implementation accepts parent-directory traversal such as .. and uses it directly when selecting the template root. As a result, a template can escape its own directory and make Copier render files from the parent directory without --UNSAFE. This issue has been patched in version 9.14.1.", "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34726.json" }, { "category": "description", "text": "Copier is a library and CLI app for rendering project templates. Prior to version 9.14.1, Copier's _subdirectory setting is documented as the subdirectory to use as the template root. However, the current implementation accepts parent-directory traversal such as .. and uses it directly when selecting the template root. As a result, a template can escape its own directory and make Copier render files from the parent directory without --UNSAFE. This issue has been patched in version 9.14.1.", "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34726" }, { "category": "other", "text": "0.00014", "title": "EPSS" }, { "category": "other", "text": "3.8", "title": "NCSC Score" }, { "category": "other", "text": "There is cwe data available from source Nvd", "title": "NCSC Score top decreasing factors" } ], "product_status": { "known_affected": [ "CSAFPID-5985269" ] }, "references": [ { "category": "external", "summary": "Source - github", "url": "https://api.github.com/advisories/GHSA-85v3-4m8g-hrh6" }, { "category": "external", "summary": "Source - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34726.json" }, { "category": "external", "summary": "Source - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34726" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd", "url": "https://github.com/copier-org/copier/security/advisories/GHSA-85v3-4m8g-hrh6" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/advisories/GHSA-85v3-4m8g-hrh6" }, { "category": "external", "summary": "Reference - cveprojectv5; nvd", "url": "https://github.com/copier-org/copier/commit/cb80a3ffc9c3787de3ed837e04ca29a0ff8ca3df" }, { "category": "external", "summary": "Reference - cveprojectv5; nvd", "url": "https://github.com/copier-org/copier/releases/tag/v9.14.1" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N", "baseScore": 4.4, "baseSeverity": "MEDIUM" }, "products": [ "CSAFPID-5985269" ] } ], "title": "CVE-2026-34726" } ] }