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Vulnerabilities

Security incident · GHSA-wf6j-7hvr-gr93

Hydra legacy target blacklist permits unsafe PyYAML loading

Published Oct 27, 2026 · catalog updated Oct 27, 2026 · Hydra legacy target blacklist

Last checked Oct 28, 2026, 11 days ago.

Open the advisory

Exploitation likelihood is not on this record for GHSA-wf6j-7hvr-gr93. A missing EPSS score is not a low risk. Compare Hydra legacy target blacklist with the linked advisory before you change production.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Hydra legacy target blacklist).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
High7.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Version ranges on file
Affected products
PyPI hydra-core · pip hydra-core

## Summary Hydra's legacy target blacklist omits PyYAML's unsafe loading surfaces. If an application passes attacker-controlled targets and arguments to instantiate(), a target such as yaml.unsafe_load can execute Python code through a config-controlled YAML stream containing Python object-construction tags. ## Impact and prerequisites The attacker must control the relevant target and arguments that the application instantiates. The configured callable executes with the application's process privileges. This is a gap in the best-effort legacy blacklist. It is not a bypass of Hydra 1.4's execution whitelist supplied by trusted Python code. One realistic exposure is a model downloaded from a third-party repository, such as Hugging Face, that bundles attacker-controlled configuration. When a victim loads the model using application code that passes this configuration to legacy Hydra instantiation without effective target restrictions, the model's metadata can execute code in the victim process. This model-loading attack pattern is documented in the original Hydra advisory GHSA-2cp2-2r3c-7p7r and the associated Unit 42 research. It does not imply that all Hugging Face models or currently patched downstream loaders are affected. Hydra 1.3's blacklist is defense in depth, not a complete security boundary. Hydra 1.4 is affected on its deprecated no-whitelist legacy path. Installed application wrappers can perform indirect operations beyond a name-based blacklist's coverage; this fix does not make arbitrary configuration safe. The unsafe_load finding is directly reproduced. PyYAML 6.0.3 full_load rejects the demonstrated python/object/apply payload, so the finding does not claim that all PyYAML loading APIs execute that payload. ## Remediation The fix blocks the yaml. target namespace except for the exact yaml.safe_load, yaml.safe_load_all, yaml.safe_dump, and yaml.safe_dump_all functions. Loader classes, constructor registration, general dump/load APIs, and other targets i

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • PyPI hydra-core1.3.6 → 1.3.8
  • PyPI hydra-core1.4.0.dev9 → 1.4.0rc3
  • pip hydra-core>= 1.3.6, < 1.3.8
  • pip hydra-core>= 1.4.0.dev9, < 1.4.0rc3

How to fix GHSA-wf6j-7hvr-gr93

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for GHSA-wf6j-7hvr-gr93. A missing EPSS score is not a low risk. Compare Hydra legacy target blacklist with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with 1.3.6 → 1.3.8, 1.4.0.dev9 → 1.4.0rc3, >= 1.3.6, < 1.3.8, >= 1.4.0.dev9, < 1.4.0rc3. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-184. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

PyYAML security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 27, 2026 · GitHub Advisory Database

    Detected

    ## Summary Hydra's legacy target blacklist omits PyYAML's unsafe loading surfaces. If an application passes attacker-controlled targets and arguments to instantiate(), a target such as yaml.unsafe_load can execute Python code through a config-controlled YAML stream containing Python object-construction tags. ## Impact and prerequisites The attacker must control the relevant target and arguments th

  2. Oct 27, 2026 · GitHub Advisory Database

    Updated

    ## Summary Hydra's legacy target blacklist omits PyYAML's unsafe loading surfaces. If an application passes attacker-controlled targets and arguments to instantiate(), a target such as yaml.unsafe_load can execute Python code through a config-controlled YAML stream containing Python object-construction tags. ## Impact and prerequisites The attacker must control the relevant target and arguments th

  3. Oct 27, 2026 · PyPA Advisory Database

    Fix available

    hydra-core fixed in 1.3.8; hydra-core fixed in 1.4.0rc3

  4. Oct 27, 2026 · PyPA Advisory Database

    Fix available

    hydra-core fixed in 1.3.8

  5. Oct 27, 2026 · PyPA Advisory Database

    Fix available

    hydra-core fixed in 1.4.0rc3

  6. Oct 27, 2026 · PyPA Advisory Database

    Updated

    ## Summary Hydra's legacy target blacklist omits PyYAML's unsafe loading surfaces. If an application passes attacker-controlled targets and arguments to instantiate(), a target such as yaml.unsafe_load can execute Python code through a config-controlled YAML stream containing Python object-construction tags. ## Impact and prerequisites The attacker must control the relevant target and arguments th

Sources

References

Freshness

Last verified in this catalog Oct 27, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • GitHub Advisory DatabaseOct 28, 2026
  • PyPA Advisory DatabaseOct 27, 2026