PyPI · hydra-core
Hydra: hydra.utils.instantiate with untrusted config can lead to code execution
hydra.utils.instantiate() resolves and calls Python objects from config. If an
application passes untrusted config to instantiate(), an attacker who controls
_target_ and its arguments can cause arbitrary code execution in the consuming
process.
Hydra is not a network service. Exploitation requires a consuming application,
library, or user workflow to load attacker-controlled config, CLI overrides, or
model metadata and pass it to hydra.utils.instantiate().
Hydra's instantiate API is designed to construct objects and call functions from configuration. For example:
component:
_target_: package.module.Class
arg: value
When this config is passed to hydra.utils.instantiate(), Hydra resolves
_target_ and calls it with the provided arguments.
This is intended for trusted application configuration. However, if untrusted
input controls _target_, the config becomes a callable-selection mechanism. A
malicious config can select a callable capable of executing code or commands and
provide attacker-controlled arguments.
This issue is the same general class of problem discussed by Unit 42 for downstream AI/ML libraries such as NVIDIA NeMo, where untrusted model metadata was passed into Hydra instantiate:
https://unit42.paloaltonetworks.com/rce-vulnerabilities-in-ai-python-libraries/
Hydra 1.3.4 includes a blacklist for some dangerous _target_ values. That
blacklist is defense-in-depth and is not a complete security boundary. The
blacklist is not present in the released hydra-core 1.3.3 package, so this
issue should not be described as a bypass of a released 1.3.3 blacklist.
A successful attack can execute code in the process that calls
hydra.utils.instantiate(). The impact is limited to the privileges and
environment of that process.
Potential impact includes:
Applications and libraries are affected when they pass untrusted or semi-trusted
config, model metadata, CLI overrides, or other externally controlled data to
hydra.utils.instantiate() without constraining which targets may be
instantiated.
Trusted application-owned configuration is not affected in the same way.
Hydra 1.3.4 hardens the existing behavior by adding a blacklist of obvious dangerous targets. It is a substantial security improvement, and users remaining on the 1.3 release line should upgrade to 1.3.4 or a newer version.
The unreleased Hydra 1.4 development line uses an allowlist-based instantiation model that fully addresses this vulnerability class. The allowlist must come from trusted application code or another trusted channel, not from the untrusted config being instantiated.
Applications that consume untrusted or semi-trusted config should not pass it
directly to hydra.utils.instantiate(). They should validate _target_ values
against a trusted allowlist before instantiation.
Is your project exposed to this? Stateward checks every dependency on every pull request and flags it only if your code actually reaches it.
Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.