low

S3 Replication only logs first destination bucket

Published Wed, Jul 20th, 2022
Platforms

Summary

If a malicious actor with prior access to an AWS environment has permission to modify the S3 Replication Service role access policy, they could abuse cross-account replication to exfiltrate stolen data to an external bucket under their control. Moreover, when configured to replicate to multiple buckets at once, the S3 Replication Service only logs a putObject event to CloudTrail for the first destination bucket. Thus, as long as the malicious actor's bucket isn't the first replication destination, their activity wouldn't be logged in CloudTrail, and might go undetected.

Affected Services

S3

Remediation

None

Tracked CVEs

No tracked CVEs

References

Disclosure Date
Tue, Oct 19th, 2021
Exploitablity Period
ongoing
Known ITW Exploitation
-
Detection Methods
Monitor for changes to Replication rules (e.g., via the S3BucketChangesAlarm alert in CloudWatch) and note any suspicious destinations.
Discovered by
Kat Traxler, null