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Vulnerability · Published Oct 6, 2026 · Assigned by GitHub_M

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

High 8.5

In plain English

A high-severity security flaw in hydra from hydra-ecosystem. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.5High
Exploit odds (30 days)0.5%top 60.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPIhydra-core1.3.7GHSA-mwj6-rfh8-7qf4
PyPIhydra-core1.4.0.dev10GHSA-mwj6-rfh8-7qf4
PyPIhydra-core1.3.7, 1.4.0.dev10PYSEC-2026-4222

Affected products (as reported)

VendorProductVersions
hydra-ecosystem hydra >= 1.3.4, < 1.3.7>= 1.4.0.dev4, < 1.4.0.dev10

Weakness: CWE-470, CWE-693 · 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

References