GHSA-c3wx-c55w-pxjq: Code Injection
Summary
Hydra passed its Python logging configuration to logging.config.dictConfig(). Python's logging configurator can resolve and invoke importable classes and factories named by configuration, including handler class values and formatter, filter, handler, queue, and listener () factories.
This logging path was not mediated by Hydra's target policy. In versions that already protected instantiate(), logging resolution bypassed those controls because it did not use instantiate().
An attacker who can control a Hydra logging configuration can use a custom class or factory to execute code with the application's privileges when Hydra configures logging.
Fix
Hydra now applies its target policy to callable resolution and invocation in Hydra-configured Python logging. It authorizes custom factories, handlers, formatters, filters, queues, listeners, aliases, discovery results, and callable results before they can be used.
Hydra 1.3.6 uses the hardened blacklist. The Hydra 1.3 blacklist is a best-effort, defense-in-depth measure. It is not a complete security boundary and does not make untrusted logging configuration safe.
Hydra 1.4.0.dev9 introduces the execution whitelist as the recommended primary boundary, with the blacklist retained as a deprecated compatibility fallback. When an execution whitelist is supplied, Hydra automatically permits targets used by its built-in logging configurations, while custom logging integrations must be explicitly authorized by trusted Python code. If no whitelist is supplied, Hydra warns and preserves legacy fallback behavior.
Remediation
Upgrade to Hydra 1.3.6, or to Hydra 1.4.0.dev9 or later when testing the 1.4 prerelease line.
On Hydra 1.3, do not compose logging configuration from untrusted sources. On Hydra 1.4 and later, constrain custom logging targets with a narrow execution whitelist supplied by trusted Python code. The execution whitelist controls callable selection; it is not general validation of all logging settings.
For Hydra 1.4 execution-whitelist configuration, see:
https://hydra.cc/docs/advanced/executionwhitelist/
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/hydra-coreto a version that resolves this vulnerability.Fixed in 1.4.0.dev9 - Upgrade
Upgrade
pip/hydra-coreto a version that resolves this vulnerability.Fixed in 1.3.6 - Upgrade
Upgrade
Hydra 1.3to a version that resolves this vulnerability.Fixed in 1.3.6 - Upgrade
Upgrade
Hydra 1.4 prerelease lineto a version that resolves this vulnerability.Fixed in 1.4.0.dev9 - Configuration
Constrain custom logging targets with a narrow execution whitelist supplied by trusted Python code.
Hydra 1.4 and later execution whitelist = narrow whitelist supplied by trusted Python code - Compensating control
On Hydra 1.3, do not compose logging configuration from untrusted sources.
Event History
Frequently Asked Questions
Who is exposed to this issue?
Applications using Hydra are exposed if an attacker can control the Hydra logging configuration that is passed to Python's logging configurator. Exploitation runs code with the affected application's privileges.
What must an attacker control to exploit it?
The attacker needs control over a Hydra logging configuration. They can specify importable classes or callable factories through logging handler classes or formatter, filter, handler, queue, listener, and related factory configuration.
Are existing instantiate() protections sufficient?
No. The vulnerable logging path did not use instantiate(), so it bypassed target-policy controls that protected instantiate().
What versions contain the stated fixes?
Hydra 1.3.6 applies a hardened blacklist to logging callable resolution. Hydra 1.4.0.dev9 introduces an execution whitelist; the provided information does not state a final 1.4 release version.
Can Hydra 1.3 make untrusted logging configurations safe?
No. The Hydra 1.3 blacklist is described as best-effort defense in depth, not a complete security boundary. Untrusted logging configuration should not be treated as safe.