Sigurd Spieckermann

7 exploits Active since Dec 2024
CVE-2026-34726 WRITEUP MEDIUM WRITEUP
Copier `_subdirectory` allows template root escape via parent-directory traversal
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.
CVSS 4.4
CVE-2026-34730 WRITEUP MEDIUM WRITEUP
Copier `_external_data` allows path traversal and absolute-path local file read without unsafe mode
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.
CVSS 5.5
CVE-2024-56201 WRITEUP HIGH WRITEUP
Jinja 3.0.0-3.1.4 - Remote Code Execution via Template Filename Control
Jinja is an extensible templating engine. In versions on the 3.x branch prior to 3.1.5, a bug in the Jinja compiler allows an attacker that controls both the content and filename of a template to execute arbitrary Python code, regardless of if Jinja's sandbox is used. To exploit the vulnerability, an attacker needs to control both the filename and the contents of a template. Whether that is the case depends on the type of application using Jinja. This vulnerability impacts users of applications which execute untrusted templates where the template author can also choose the template filename. This vulnerability is fixed in 3.1.5.
CVSS 8.8
CVE-2025-55201 WRITEUP HIGH WRITEUP
Copier < 9.9.1 - Path Traversal via Unconstrained Pathlib Path Objects
Copier library and CLI app for rendering project templates. Prior to 9.9.1, a safe template can currently read and write arbitrary files because Copier exposes a few pathlib.Path objects in the Jinja context which have unconstrained I/O methods. This effectively renders the security model w.r.t. filesystem access useless. This vulnerability is fixed in 9.9.1.
CVE-2025-55214 WRITEUP MEDIUM WRITEUP
Copier 7.1.0-9.9.0 - Path Traversal and Arbitrary File Write via Pathjoin Filter
Copier library and CLI app for rendering project templates. From 7.1.0 to before 9.9.1, Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use unsafe features like custom Jinja extensions which would require passing the --UNSAFE,--trust flag. As it turns out, a safe template can currently write files outside the destination path where a project shall be generated or updated. This is possible when rendering a generated directory structure whose rendered path is either a relative parent path or an absolute path. Constructing such paths is possible using Copier's builtin pathjoin Jinja filter and its builtin _copier_conf.sep variable, which is the platform-native path separator. This way, a malicious template author can create a template that overwrites arbitrary files (according to the user's write permissions), e.g., to cause havoc. This vulnerability is fixed in 9.9.1.
CVE-2026-23968 WRITEUP MEDIUM WRITEUP
copier < 9.11.2 - Arbitrary File Access via Symlink Following
Copier is a library and CLI app for rendering project templates. Prior to version 9.11.2, Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use 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` (which is Copier's default setting). Version 9.11.2 patches the issue.
CVSS 5.5
CVE-2026-23986 WRITEUP HIGH WRITEUP
copier < 9.11.2 - Arbitrary File Write via Symlink Following with _preserve_symlinks
Copier is a library and CLI app for rendering project templates. Prior to version 9.11.2, Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use unsafe features like custom Jinja extensions which would require passing the `--UNSAFE,--trust` flag. As it turns out, a safe template can currently write to arbitrary directories outside the destination path by using directory a symlink along with `_preserve_symlinks: true` and a generated directory structure whose rendered path is inside the symlinked directory. This way, a malicious template author can create a template that overwrites arbitrary files (according to the user's write permissions), e.g., to cause havoc. Version 9.11.2 patches the issue.
CVSS 7.1