The vulnerability is in OpenStack Swift 2.38.0 or earlier, where the S3API middleware fails to sanitize Swift-native control headers (X‑Copy‑From, X‑Copy‑From‑Account) when the s3_acl option is enabled. An attacker who can create a signed PUT request to their own bucket can inject these headers and instruct Swift to perform a server‑side copy from a private object belonging to another tenant. Because the middleware has already authorized the destination request, the source object’s ACL is bypassed, allowing the attacker to read any object whose project_id, container name, and object name are known, regardless of the source object’s ownership.

OpenStack Swift implementations running version 2.38.0 or any earlier release are impacted. The issue is present only when the s3_acl configuration is set to true, which is not the default but may be enabled in certain deployments.

The CVSS score of 6.0 indicates a moderate severity. The EPSS score is not available and the vulnerability is not listed in CISA KEV, suggesting that widespread exploitation has not yet been observed. However, the attack requires the attacker to know the target object’s identifiers and to have the ability to submit a signed S3 request to their own bucket. The attacker can then retrieve the contents of the source object, effectively bypassing tenant isolation and enabling unauthorized data disclosure.