{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/lxc/incus/v6"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.1.0"
            },
            {
              "last_affected": "6.20.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/lxc/incus/v6"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "6.0.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-23953"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-93"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-22T20:21:17Z",
    "nvd_published_at": "2026-01-22T22:16:20Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nA user with the ability to launch a container with a custom YAML configuration (e.g a member of the \u2018incus\u2019 group) can create an environment variable containing newlines, which can be used to add additional configuration items in the container\u2019s `lxc.conf` due to the newline injection. This can allow adding arbitrary lifecycle hooks, ultimately resulting in arbitrary command execution on the host.\n\n### Details\nWhen passing environment variables in the config block of a new container, values are not checked for the presence of newlines [1], which can result in newline injection inside the generated container `lxc.conf`. This can be used to set arbitrary additional configuration items, such as `lxc.hook.pre-start`. By exploiting this, a user with the ability to launch a container with an arbitrary config can achieve arbitrary command execution as root on the host.\n\nExploiting this issue on IncusOS requires a slight modification of the payload to change to a different writable directory for the validation step (e.g /tmp). This can be confirmed with a second container with /tmp mounted from the host (A privileged action for validation only).\n\n[1] https://github.com/lxc/incus/blob/HEAD/internal/server/instance/drivers/driver_lxc.go#L1081\n\n### PoC\nA proof-of-concept script exploiting this vulnerability can be found attached, named environment_newline_injection.sh, showing arbitrary command execution, which will write a file to the root filesystem (`/newline_injection_command_exec_poc`)\n\nManual Reproduction steps:\n1. Launch a new container with a configuration file containing a multiline YAML string as an environment variable value, such as in the listing below.\n2. Observe that the lxc.conf (`/run/incus/user-1000_poc/lxc.conf` in my case) contains an additional `lxc.hook.pre-start` item\n3. Observe the creation of the file in the host root directory, with contents proving command execution as root.\n\n```\nincus launch images:alpine/edge --ephemeral poc \u003c\u003c EOF\nconfig:\n  environment.FOO: |-\n    abc\n    lxc.hook.pre-start = /bin/sh -c \"id \u003e /newline_injection_command_exec_poc\"\nEOF\n```\n\n### Impact\nA user with the ability to launch a container with a custom YAML configuration (e.g a member of the \u2018incus\u2019 group) can achieve arbitrary command execution on the host.\n\n### Attachments\n[environment_newline_injection.sh](https://github.com/user-attachments/files/24473682/environment_newline_injection.sh)\n[environment_newline_injection.patch](https://github.com/user-attachments/files/24473685/environment_newline_injection.patch)",
  "id": "GHSA-x6jc-phwx-hp32",
  "modified": "2026-01-23T15:46:26Z",
  "published": "2026-01-22T20:21:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lxc/incus/security/advisories/GHSA-x6jc-phwx-hp32"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23953"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lxc/incus"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lxc/incus/blob/HEAD/internal/server/instance/drivers/driver_lxc.go#L1081"
    },
    {
      "type": "WEB",
      "url": "https://github.com/user-attachments/files/24473682/environment_newline_injection.sh"
    },
    {
      "type": "WEB",
      "url": "https://github.com/user-attachments/files/24473685/environment_newline_injection.patch"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Incus container environment configuration newline injection"
}