Hydra: Mutable instantiate policy sets allow target blocklist bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.5 · CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-106439: 0.46% estimated exploitation activity in the next 30 days; percentile 39.68 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Hydra's legacy instantiate() target blocklists and related execution-policy collections are stored in mutable module-level state. Because locate() can resolve attributes on imported objects, a configuration can resolve a mutation method such as .discard(), modify the active policy, and then instantiate a target that would otherwise be blocked. Impact A configuration controlling multiple sibling target entries can first remove an entry from a target blocklist and then invoke the removed target. Sibling nodes are processed in insertion order and consult the same mutable module-level policy. This affects the legacy/default path without an execution whitelist. The 1.3 blocklist is a defense-in-depth measure rather than a complete security boundary, and applications must not treat arbitrary untrusted configuration as safe to instantiate or use for Python logging configuration. Released hydra-core versions 1.3.4 through 1.3.6 and 1.4.0.dev4 through 1.4.0.dev9 are affected. Fixed…

Published by the source

7 Oct 2026, 20:23 UTC

Last modified by the source

7 Oct 2026, 20:23 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-mwj6-rfh8-7qf4

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# Patch Next advisory brief: CVE-2026-106439

Advisory: Hydra: Mutable instantiate policy sets allow target blocklist bypass
IDs: CVE-2026-106439, GHSA-mwj6-rfh8-7qf4
Record: https://patchnext.com/advisories/cve-2026-106439 (revision 1, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hydra-core 1.4.0.dev10, 1.3.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI hydra-core: affected >= 1.3.4, < 1.3.7; >= 1.4.0.dev4, < 1.4.0.dev10; fixed in 1.3.7, 1.4.0.dev10

## Suggested inspection (read-only)
- `python -m pip show hydra-core`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on hydra-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-mwj6-rfh8-7qf4 (GitHub-reviewed advisory GHSA-mwj6-rfh8-7qf4 lists affected ranges: PyPI hydra-core >=1.3.4 =1.4.0.dev4 <1.4.0.dev10)

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