CVE-2026-106439: Hydra Package Vulnerability Allows Target Blocklist Bypass
Summary
CVE-2026-106439: Hydra: Mutable instantiate policy sets allow target blocklist bypass. Affects hydra-core across 2 version ranges.
>= 1.3.4, < 1.3.7
>= 1.4.0.dev4, < 1.4.0.dev10
Fixed in 1.3.7 or 1.4.0.dev10, depending on the release line you run. How to fix ↓
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Background
Hydra is a popular framework for building complex applications in Python, enabling users to compose and manage configurations effectively. It leverages a modular architecture that allows for dynamic instantiation of components based on user-defined configurations. However, a significant vulnerability has been identified in certain versions of the hydra-core package, which could lead to unauthorized execution of code due to mutable state management.
Vulnerability Detail
The vulnerability arises from Hydra's legacy instantiate target blocklists and execution-policy collections being stored in mutable module-level state. This allows an attacker to manipulate the blocklist by using methods like .discard() to remove entries, thereby bypassing security measures. The impact is severe as it enables unauthorized access to potentially harmful targets, especially when configurations are sourced from untrusted inputs. The vulnerability affects versions 1.3.4 to 1.3.6 and 1.4.0.dev4 to 1.4.0.dev9 of hydra-core, posing a high risk to applications relying on these versions.
How To Fix
Latest published version: 1.4.0.dev10 as of 23 Oct 2026
pip install --upgrade "hydra-core==1.4.0.dev10"The newest release already contains this fix.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
>= 1.3.4, < 1.3.71.3.7pip install --upgrade "hydra-core==1.3.7"
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Workaround
As a temporary measure, avoid passing configuration from untrusted sources to the instantiate() function or to Hydra-controlled Python logging configuration. For affected 1.4 development releases, you can supply a trusted, narrowly scoped execution whitelist from Python code. Ensure that the whitelist itself is not derived from untrusted configuration.
Conclusion
The vulnerability CVE-2026-106439 in the hydra-core package poses a significant risk due to its ability to bypass target blocklists. Users are strongly advised to upgrade to the fixed versions to mitigate this risk. Additionally, implementing workarounds can provide temporary relief until an upgrade is feasible.
See every vulnerability recorded for hydra-core →
FAQ
CVE-2026-106439 is a vulnerability in the hydra-core package that allows attackers to bypass target blocklists, potentially leading to unauthorized code execution.
The affected versions are hydra-core 1.3.4 through 1.3.6 and 1.4.0.dev4 through 1.4.0.dev9.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The CVSS score of this vulnerability is 8.5, indicating a high severity level.
If you cannot upgrade immediately, restrict configuration input to trusted sources and avoid using untrusted configurations.
References
Related vulnerabilities
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