CVE-2026-107716

Banks generates meaningful LLM prompts using a simple template language. Prior to 2.5.1, Banks DirectoryPromptRegistry does not reject symbolic links for index.json or discovered and existing .jinja prompt files. In an application where untrusted users can influence a prompt directory, DirectoryPromptRegistry._scan() and DirectoryPromptRegistry.get() can follow a link outside the registry root and disclose a file, while DirectoryPromptRegistry.set(), DirectoryPromptRegistry._save(), and DirectoryPromptRegistry._load() can read or overwrite an external link target. The issue requires attacker influence over the registry directory or its extracted contents. This issue is fixed in version 2.5.1.

Banks generates meaningful LLM prompts using a simple template language. Prior to 2.5.1, Banks DirectoryPromptRegistry does not reject symbolic links for index.json or discovered and existing .jinja prompt files. In an application where untrusted users can influence a prompt directory, DirectoryPromptRegistry._scan() and DirectoryPromptRegistry.get() can follow a link outside the registry root and disclose a file, while DirectoryPromptRegistry.set(), DirectoryPromptRegistry._save(), and DirectoryPromptRegistry._load() can read or overwrite an external link target. The issue requires attacker influence over the registry directory or its extracted contents. This issue is fixed in version 2.5.1.

Summary

In banks.registries.DirectoryPromptRegistry, prompt file paths and the index file (index.json) do not refuse symbolic links. When a prompt directory contains or accepts untrusted files (e.g. unpacked archives, shared repositories, or multi-tenant folders), symbolic links pointing outside the registry root can be used to disclose arbitrary files via _scan() / get() or overwrite arbitrary files via set() / _save().

Details

Following PR #77, DirectoryPromptRegistry validates path resolution for prompt names. However:

1. self._index_path (index.json) is not checked for symbolic links. A symlink pointing to an external target (e.g. a configuration file) will be overwritten by _save() upon reg.set(), or read via _load().
2. In _scan(), discovered .jinja files are opened and indexed without checking if path.is_symlink() or if the resolved path escapes the registry root. A symlink pointing to a sensitive file outside the root is read and indexed.
3. In set(), prompt_file.write_text(...) is called without checking if prompt_file is an existing symbolic link pointing outside the root.

Impact

Arbitrary file disclosure (CWE-59 / CWE-200) and arbitrary file overwrite (CWE-59) in applications where prompt directories can be influenced by untrusted users or extracted from archives.

Proof of Concept

import os
from pathlib import Path
from banks.registries.directory import DirectoryPromptRegistry, DEFAULT_INDEX_NAME
from banks.prompt import Prompt

# Disclose external file via symlink in prompt directory
reg_dir = Path("/tmp/registry")
reg_dir.mkdir(exist_ok=True)
secret = Path("/tmp/secret.txt")
secret.write_text("SECRET_API_TOKEN")

os.symlink(secret, reg_dir / "leak.0.jinja")
reg = DirectoryPromptRegistry(reg_dir, force_reindex=True)
print("Disclosed content:", reg.get(name="leak", version="0").raw)

# Overwrite external file via symlink index
target = Path("/tmp/target.conf")
target.write_text("ORIGINAL")
(reg_dir / DEFAULT_INDEX_NAME).unlink(missing_ok=True)
os.symlink(target, reg_dir / DEFAULT_INDEX_NAME)
reg.set(prompt=Prompt("pwn", name="test", version="1"))
print("Target overwritten:", target.read_text())

Remediation

1. In _validate_index_path(): verify _index_path is not a symlink and resolves within _path.
2. In _scan(): reject path.is_symlink() and check path.resolve().is_relative_to(root).
3. In set(): reject existing symbolic links before writing.

A tested fix and regression tests have been prepared and pushed to: https://github.com/jankesec/banks/tree/fix-directory-registry-symlinks-and-nesting

Banks generates meaningful LLM prompts using a simple template language. Prior to 2.5.1, Banks DirectoryPromptRegistry does not reject symbolic links for index.json or discovered and existing .jinja prompt files. In an application where untrusted users can influence a prompt directory, DirectoryPromptRegistry._scan() and DirectoryPromptRegistry.get() can follow a link outside the registry root and disclose a file, while DirectoryPromptRegistry.set(), DirectoryPromptRegistry._save(), and DirectoryPromptRegistry._load() can read or overwrite an external link target. The issue requires attacker influence over the registry directory or its extracted contents. This issue is fixed in version 2.5.1.

Banks generates meaningful LLM prompts using a simple template language. Prior to 2.5.1, Banks DirectoryPromptRegistry does not reject symbolic links for index.json or discovered and existing .jinja prompt files. In an application where untrusted users can influence a prompt directory, DirectoryPromptRegistry._scan() and DirectoryPromptRegistry.get() can follow a link outside the registry root and disclose a file, while DirectoryPromptRegistry.set(), DirectoryPromptRegistry._save(), and DirectoryPromptRegistry._load() can read or overwrite an external link target. The issue requires attacker influence over the registry directory or its extracted contents. This issue is fixed in version 2.5.1.

Summary

In banks.registries.DirectoryPromptRegistry, prompt file paths and the index file (index.json) do not refuse symbolic links. When a prompt directory contains or accepts untrusted files (e.g. unpacked archives, shared repositories, or multi-tenant folders), symbolic links pointing outside the registry root can be used to disclose arbitrary files via _scan() / get() or overwrite arbitrary files via set() / _save().

Details

Following PR #77, DirectoryPromptRegistry validates path resolution for prompt names. However:

1. self._index_path (index.json) is not checked for symbolic links. A symlink pointing to an external target (e.g. a configuration file) will be overwritten by _save() upon reg.set(), or read via _load().
2. In _scan(), discovered .jinja files are opened and indexed without checking if path.is_symlink() or if the resolved path escapes the registry root. A symlink pointing to a sensitive file outside the root is read and indexed.
3. In set(), prompt_file.write_text(...) is called without checking if prompt_file is an existing symbolic link pointing outside the root.

Impact

Arbitrary file disclosure (CWE-59 / CWE-200) and arbitrary file overwrite (CWE-59) in applications where prompt directories can be influenced by untrusted users or extracted from archives.

Proof of Concept

import os
from pathlib import Path
from banks.registries.directory import DirectoryPromptRegistry, DEFAULT_INDEX_NAME
from banks.prompt import Prompt

# Disclose external file via symlink in prompt directory
reg_dir = Path("/tmp/registry")
reg_dir.mkdir(exist_ok=True)
secret = Path("/tmp/secret.txt")
secret.write_text("SECRET_API_TOKEN")

os.symlink(secret, reg_dir / "leak.0.jinja")
reg = DirectoryPromptRegistry(reg_dir, force_reindex=True)
print("Disclosed content:", reg.get(name="leak", version="0").raw)

# Overwrite external file via symlink index
target = Path("/tmp/target.conf")
target.write_text("ORIGINAL")
(reg_dir / DEFAULT_INDEX_NAME).unlink(missing_ok=True)
os.symlink(target, reg_dir / DEFAULT_INDEX_NAME)
reg.set(prompt=Prompt("pwn", name="test", version="1"))
print("Target overwritten:", target.read_text())

Remediation

1. In _validate_index_path(): verify _index_path is not a symlink and resolves within _path.
2. In _scan(): reject path.is_symlink() and check path.resolve().is_relative_to(root).
3. In set(): reject existing symbolic links before writing.

A tested fix and regression tests have been prepared and pushed to: https://github.com/jankesec/banks/tree/fix-directory-registry-symlinks-and-nesting

Summary

In banks.registries.DirectoryPromptRegistry, prompt file paths and the index file (index.json) do not refuse symbolic links. When a prompt directory contains or accepts untrusted files (e.g. unpacked archives, shared repositories, or multi-tenant folders), symbolic links pointing outside the registry root can be used to disclose arbitrary files via _scan() / get() or overwrite arbitrary files via set() / _save().

Details

Following PR #77, DirectoryPromptRegistry validates path resolution for prompt names. However:

1. self._index_path (index.json) is not checked for symbolic links. A symlink pointing to an external target (e.g. a configuration file) will be overwritten by _save() upon reg.set(), or read via _load().
2. In _scan(), discovered .jinja files are opened and indexed without checking if path.is_symlink() or if the resolved path escapes the registry root. A symlink pointing to a sensitive file outside the root is read and indexed.
3. In set(), prompt_file.write_text(...) is called without checking if prompt_file is an existing symbolic link pointing outside the root.

Impact

Arbitrary file disclosure (CWE-59 / CWE-200) and arbitrary file overwrite (CWE-59) in applications where prompt directories can be influenced by untrusted users or extracted from archives.

Proof of Concept

import os
from pathlib import Path
from banks.registries.directory import DirectoryPromptRegistry, DEFAULT_INDEX_NAME
from banks.prompt import Prompt

# Disclose external file via symlink in prompt directory
reg_dir = Path("/tmp/registry")
reg_dir.mkdir(exist_ok=True)
secret = Path("/tmp/secret.txt")
secret.write_text("SECRET_API_TOKEN")

os.symlink(secret, reg_dir / "leak.0.jinja")
reg = DirectoryPromptRegistry(reg_dir, force_reindex=True)
print("Disclosed content:", reg.get(name="leak", version="0").raw)

# Overwrite external file via symlink index
target = Path("/tmp/target.conf")
target.write_text("ORIGINAL")
(reg_dir / DEFAULT_INDEX_NAME).unlink(missing_ok=True)
os.symlink(target, reg_dir / DEFAULT_INDEX_NAME)
reg.set(prompt=Prompt("pwn", name="test", version="1"))
print("Target overwritten:", target.read_text())

Remediation

1. In _validate_index_path(): verify _index_path is not a symlink and resolves within _path.
2. In _scan(): reject path.is_symlink() and check path.resolve().is_relative_to(root).
3. In set(): reject existing symbolic links before writing.

A tested fix and regression tests have been prepared and pushed to: https://github.com/jankesec/banks/tree/fix-directory-registry-symlinks-and-nesting