Executive brief
AWS Systems Manager Agent is software that runs on EC2 instances and on-premises servers to enable cloud-based management and configuration. A path traversal flaw in the file download feature allows an authenticated attacker to write arbitrary files with root-level privileges by exploiting improper input validation on S3 object keys. An attacker could overwrite sensitive system files and achieve remote code execution on affected instances.
Technical details
The vulnerability is a path traversal (CWE-22) in the aws:downloadContent plugin of amazon-ssm-agent prior to version 3.3.4515.0. The root cause is improper limitation of a pathname to a restricted directory when processing S3 object keys. An authenticated remote user with ssm:SendCommand permission restricted to the AWS-DownloadContent document can exploit this by crafting malicious object keys containing path traversal sequences (e.g., "../") to write files outside the intended download directory with root privileges. The attack requires the attacker to have AWS IAM permissions to invoke Systems Manager SendCommand with the AWS-DownloadContent document. Successful exploitation can lead to arbitrary code execution as root if critical system files are overwritten. The fix is available in version 3.3.4515.0 and later.
Affected products
- Amazon Systems Manager Agent (amazon-ssm-agent) 2.0.767.0 to 3.3.4364.0
Timeline
- 2026-08-28: disclosed: AWS Security Bulletin 2026-091 published
- 2026-08-28: patched: Fix available in version 3.3.4515.0