Summary
pydantic-settings: NestedSecretsSettingsSource follows symlinks outside secretsdir, enabling local file read and bypassing secretsdirmaxsize
NestedSecretsSettingsSource reads secret values from files in a configured secrets_dir. When secrets_nested_subdir=True, a directory entry inside secrets_dir that is a symbolic link pointing outside secrets_dir is followed, so files outside the configured directory are read into settings values. The same code path bypasses the documented secrets_dir_max_size protection. An attacker or lower-privileged component able to influence entries in the configured secrets directory (for example, a writable or shared secrets mount) can turn this into an unintended local file read into settings and can defeat the advertised loading-size cap. This report does not claim network reachability by itself.
Details
NestedSecretsSettingsSource performed two passes over secrets_dir using two different, inconsistent directory-traversal implementations:
- The size check in
validate_secrets_path()usedPath.glob('**/*'), which does not descend into a symbolically-linked directory. - The loader in
load_secrets()usedglob.iglob(f'{path}/**/*', recursive=True)followed byread_text(), which does follow symlinked directories and reads through the link target.
Because the two passes disagreed on symlinks, a symlinked directory inside secrets_dir whose target lives elsewhere was invisible to the size accounting (counted as 0 bytes) while still being fully read by the loader. This produces two distinct problems:
- Out-of-tree read (CWE-22 / CWE-59). A symlinked directory (or file) inside
secrets_dirthat resolves outside it is followed, and the external file's contents are loaded into the corresponding settings field. secrets_dir_max_sizebypass (CWE-400). The size check never sees the out-of-tree content, so the documented size cap is neither respected nor able to reject the oversized external file. A related amplification exists for cyclic in-tree symlinks, whichglob.iglob(recursive=True)re-traverses, inflating the size accounting and the number of loaded secrets.
Reproduction
In a clean Linux container, with a secrets_dir containing a symlink secrets/db -> /path/outside and an outside/passwd file of 512 bytes, while secrets_dir_max_size=100:
from pydantic import BaseModel
from pydantic_settings import (
BaseSettings,
SettingsConfigDict,
NestedSecretsSettingsSource,
)
class Db(BaseModel):
passwd: str | None = None
class Settings(BaseSettings):
model_config = SettingsConfigDict(
secrets_dir='secrets',
secrets_nested_subdir=True,
secrets_dir_max_size=100, # outside/passwd is 512 bytes
)
db: Db = Db()
@classmethod
def settings_customise_sources(
cls, settings_cls, init_settings, env_settings, dotenv_settings, file_secret_settings
):
return (NestedSecretsSettingsSource(file_secret_settings),)
On affected versions, Settings().db.passwd is populated with the 512-byte out-of-tree file and no SettingsError is raised, even though the file exceeds secrets_dir_max_size.
Mitigation
Upgrade to pydantic-settings 2.14.2, which:
- walks the secrets directory explicitly and only descends into directories whose resolved path stays within
secrets_dir, so symlinked directories pointing outside are never followed; - uses a single, cycle-safe iterator for both the size check and the loader, so the size accounting and the loaded set are always consistent and each real directory is visited at most once;
- skips any file whose resolved path escapes
secrets_dir, as defense in depth.
If upgrading is not immediately possible, ensure the configured secrets_dir is fully owned and controlled by the application (no writable or attacker-influenced entries), or avoid secrets_nested_subdir=True.
Impact
Applications that opt into NestedSecretsSettingsSource with secrets_nested_subdir=True and load secrets from a directory whose entries can be influenced by an attacker or a lower-privileged component (for example, a writable or shared secrets mount, or a secrets directory partially populated from untrusted input) are affected. The impact is:
- Confidentiality: files outside the configured
secrets_dircan be read into settings values (local file read). - Integrity / availability of the safeguard: the advertised
secrets_dir_max_sizecap can be bypassed, and cyclic symlinks can inflate resource usage during loading.
The vulnerability requires the ability to place a symbolic link inside the configured secrets directory; it is not remotely reachable on its own. Applications that do not use NestedSecretsSettingsSource, or that point secrets_dir at a directory fully under the application's control, are not affected.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
GHSA-4XGF-CPJX-PC3J has a CVSS score of 5.3 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.14.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Frequently Asked Questions
- What is GHSA-4XGF-CPJX-PC3J? GHSA-4XGF-CPJX-PC3J is a medium-severity path traversal vulnerability in pydantic-settings (pip), affecting versions >= 2.12.0, < 2.14.2. It is fixed in 2.14.2. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is GHSA-4XGF-CPJX-PC3J? GHSA-4XGF-CPJX-PC3J has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of pydantic-settings are affected by GHSA-4XGF-CPJX-PC3J? pydantic-settings (pip) versions >= 2.12.0, < 2.14.2 is affected.
- Is there a fix for GHSA-4XGF-CPJX-PC3J? Yes. GHSA-4XGF-CPJX-PC3J is fixed in 2.14.2. Upgrade to this version or later.
- Is GHSA-4XGF-CPJX-PC3J exploitable, and should I be worried? Whether GHSA-4XGF-CPJX-PC3J is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-4XGF-CPJX-PC3J is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-4XGF-CPJX-PC3J? Upgrade
pydantic-settingsto 2.14.2 or later.