Publish GHSA-xjhm-gp88-8pfx

Author: advisory-database[bot]

advisories/github-reviewed/2026/01/GHSA-xjhm-gp88-8pfx/GHSA-xjhm-gp88-8pfx.json

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+{
+  "schema_version": "1.4.0",
+  "id": "GHSA-xjhm-gp88-8pfx",
+  "modified": "2026-01-21T22:08:48Z",
+  "published": "2026-01-21T22:08:48Z",
+  "aliases": [
+    "CVE-2026-23968"
+  ],
+  "summary": "Copier safe template has arbitrary filesystem read access via symlinks when _preserve_symlinks: false",
+  "details": "### Impact\n\nCopier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use [unsafe](https://copier.readthedocs.io/en/stable/configuring/#unsafe) features like custom Jinja extensions which would require passing the `--UNSAFE,--trust` flag. As it turns out, a safe template can currently include arbitrary files/directories outside the local template clone location by using symlinks along with [`_preserve_symlinks: false`](https://copier.readthedocs.io/en/stable/configuring/#preserve_symlinks) (which is Copier's default setting). \n\nImagine, e.g., a malicious template author who creates a template that reads SSH keys or other secrets from well-known locations and hopes for a user to push the generated project to a public location like [github.com](https://github.com/) where the template author can extract the secrets.\n\nReproducible example:\n\n- Illegally include a file in the generated project via symlink resolution:\n\n    ```shell\n    echo \"s3cr3t\" > secret.txt\n\n    mkdir src/\n    pushd src/\n    ln -s ../secret.txt stolen-secret.txt\n    popd\n\n    uvx copier copy src/ dst/\n\n    cat dst/stolen-secret.txt\n    #s3cr3t\n    ```\n\n- Illegally include a directory in the generated project via symlink resolution:\n\n    ```shell\n    mkdir secrets/\n    pushd secrets/\n    echo \"s3cr3t\" > secret.txt\n    popd\n\n    mkdir src/\n    pushd src/\n    ln -s ../secrets stolen-secrets\n    popd\n\n    uvx copier copy src/ dst/\n\n    tree dst/\n    # dst/\n    # └── stolen-secrets\n    #     └── secret.txt\n    #\n    # 1 directory, 1 file\n    cat dst/stolen-secrets/secret.txt\n    # s3cr3t\n    ```\n\n### Patches\n\nn/a\n\n### Workarounds\n\nn/a\n\n### References\n\nn/a",
+  "severity": [
+    {
+      "type": "CVSS_V4",
+      "score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"
+    }
+  ],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "PyPI",
+        "name": "copier"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "0"
+            },
+            {
+              "fixed": "9.11.2"
+            }
+          ]
+        }
+      ]
+    }
+  ],
+  "references": [
+    {
+      "type": "WEB",
+      "url": "https://github.com/copier-org/copier/security/advisories/GHSA-xjhm-gp88-8pfx"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/copier-org/copier/commit/b3a7b3772d17cf0e7a4481978188c9f536c8d8f6"
+    },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/copier-org/copier"
+    }
+  ],
+  "database_specific": {
+    "cwe_ids": [
+      "CWE-61"
+    ],
+    "severity": "MODERATE",
+    "github_reviewed": true,
+    "github_reviewed_at": "2026-01-21T22:08:48Z",
+    "nvd_published_at": null
+  }
+}