CVE-2026-68508: Hydra Hydra.utils.instantiate With Untrusted Config Can Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2cp2-2r3c-7p7r",
  "modified" : "2026-08-21T20:57:31Z",
  "published" : "2026-08-21T20:57:31Z",
  "aliases" : [ "CVE-2026-68508" ],
  "summary" : "Hydra: hydra.utils.instantiate with untrusted config can lead to code execution",
  "details" : "## Summary\n\n`hydra.utils.instantiate()` resolves and calls Python objects from config. If an\napplication passes untrusted config to `instantiate()`, an attacker who controls\n`_target_` and its arguments can cause arbitrary code execution in the consuming\nprocess.\n\nHydra is not a network service. Exploitation requires a consuming application,\nlibrary, or user workflow to load attacker-controlled config, CLI overrides, or\nmodel metadata and pass it to `hydra.utils.instantiate()`.\n\n## Details\n\nHydra's instantiate API is designed to construct objects and call functions from\nconfiguration. For example:\n\n```yaml\ncomponent:\n  _target_: package.module.Class\n  arg: value\n```\n\nWhen this config is passed to `hydra.utils.instantiate()`, Hydra resolves\n`_target_` and calls it with the provided arguments.\n\nThis is intended for trusted application configuration. However, if untrusted\ninput controls `_target_`, the config becomes a callable-selection mechanism. A\nmalicious config can select a callable capable of executing code or commands and\nprovide attacker-controlled arguments.\n\nThis issue is the same general class of problem discussed by Unit 42 for\ndownstream AI/ML libraries such as NVIDIA NeMo, where untrusted model metadata\nwas passed into Hydra instantiate:\n\nhttps://unit42.paloaltonetworks.com/rce-vulnerabilities-in-ai-python-libraries/\n\nHydra 1.3.4 includes a blacklist for some dangerous `_target_` values. That\nblacklist is defense-in-depth and is not a complete security boundary. The\nblacklist is not present in the released `hydra-core` 1.3.3 package, so this\nissue should not be described as a bypass of a released 1.3.3 blacklist.\n\n## Impact\n\nA successful attack can execute code in the process that calls\n`hydra.utils.instantiate()`. The impact is limited to the privileges and\nenvironment of that process.\n\nPotential impact includes:\n\n- Reading files, credentials, environment variables, or data accessible to the\n  process\n- Modifying files, outputs, checkpoints, or application state writable by the\n  process\n- Terminating or disrupting the process\n\n## Affected Usage\n\nApplications and libraries are affected when they pass untrusted or semi-trusted\nconfig, model metadata, CLI overrides, or other externally controlled data to\n`hydra.utils.instantiate()` without constraining which targets may be\ninstantiated.\n\nTrusted application-owned configuration is not affected in the same way.\n\n## Remediation\n\nHydra 1.3.4 hardens the existing behavior by adding a blacklist of obvious\ndangerous targets. It is a substantial security improvement, and users remaining\non the 1.3 release line should upgrade to 1.3.4 or a newer version.\n\nThe unreleased Hydra 1.4 development line uses an allowlist-based instantiation\nmodel that fully addresses this vulnerability class. The allowlist must come\nfrom trusted application code or another trusted channel, not from the untrusted\nconfig being instantiated.\n\nApplications that consume untrusted or semi-trusted config should not pass it\ndirectly to `hydra.utils.instantiate()`. They should validate `_target_` values\nagainst a trusted allowlist before instantiation.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "hydra-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.3.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.3.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/hydra-ecosystem/hydra/security/advisories/GHSA-2cp2-2r3c-7p7r"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hydra-ecosystem/hydra/issues/3259"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hydra-ecosystem/hydra/pull/3261"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hydra-ecosystem/hydra/commit/7faad0dcedfb4c0a364aa1067c0080fd6fdf8dca"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/hydra-ecosystem/hydra"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hydra-ecosystem/hydra/releases/tag/v1.3.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-470", "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-21T20:57:31Z",
    "nvd_published_at" : null
  }
}