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

> Attackers can bypass execution policy blocklists in Hydra by mutating global state, enabling arbitrary code execution with application privileges.

- **Severity:** High 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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 6 Oct 2026
- **Also known as:** GHSA-mwj6-rfh8-7qf4, PYSEC-2026-4222

## What is CVE-2026-106439?

CVE-2026-106439 is a high-severity vulnerability in hydra-ecosystem hydra, published on 6 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-693 (Protection Mechanism Failure), CWE-470 (Use of Externally-Controlled Input to Select Classes or Code)

## Which versions are affected by CVE-2026-106439?

5 open source packages ship an affected version, including hydra-core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hydra-core` | PyPI | From 1.3.4 | 1.3.7, 1.4.0.dev10 |
| `hydra-core` | PyPI | From 1.3.4 | 1.3.7 |
| `hydra-core` | PyPI | From 1.3.4 | 1.3.7 |
| `hydra-core` | PyPI | From 1.4.0.dev4 | 1.4.0.dev10 |
| `hydra-core` | PyPI | From 1.4.0.dev4 | 1.4.0.dev10 |

## How do I fix CVE-2026-106439?

Upgrade hydra-core to a fixed version for your release line: 1.3.7 or 1.4.0.dev10.

## Is CVE-2026-106439 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-106439 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-106439 and fix it if it is affected.

What it is: CVE-2026-106439 is a high-severity vulnerability in hydra-ecosystem hydra, published on 6 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-106439 exists.

Affected packages and fixed versions:
- hydra-core (PyPI): affected from 1.3.4; fixed in 1.3.7, 1.4.0.dev10
- hydra-core (PyPI): affected from 1.3.4; fixed in 1.3.7
- hydra-core (PyPI): affected from 1.3.4; fixed in 1.3.7
- hydra-core (PyPI): affected from 1.4.0.dev4; fixed in 1.4.0.dev10
- hydra-core (PyPI): affected from 1.4.0.dev4; fixed in 1.4.0.dev10

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-106439/ (Markdown: https://insights.sbomify.com/CVE-2026-106439/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-106439
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-106439
- OSV: https://osv.dev/vulnerability/CVE-2026-106439

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-106439/
Summaries are generated and may contain mistakes; the official description above is the record.