Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-28T15:00:00 openstack-swift: openstack-swift: S3API presigned URL unsigned header authorization bypass 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N CWE-863

In OpenStack Swift through 2.38.0, S3API middleware does not enforce that semantic x-amz-* headers are covered by the SigV4 signature on presigned URL requests. An attacker who obtains a presigned PUT URL can inject an unsigned X-Amz-Copy-Source header, causing Swift to perform a server-side copy from an arbitrary source object using the signer's authorization context. The attacker can read any object the signer has access to, provided the target project_id, container name, and object name are known. This affects all deployments using the default s3_acl=false configuration.

A flaw was found in the S3API middleware of OpenStack Swift. The SigV4 presigned URL implementation does not require that semantic x-amz-* headers be included in the request signature. An attacker who obtains a presigned PUT URL can inject unsigned headers such as X-Amz-Copy-Source to copy objects from the signer's storage, bypassing the intended scope of the presigned URL authorization. The attacker needs prior knowledge of the target project_id, container name, and object name.

Red Hat OpenStack Platform (RHOSP) and Red Hat OpenStack Services on OpenShift (RHOSO) ship openstack-swift and are affected by this vulnerability. In default RHOSO deployments, the s3api filter is included in the active proxy-server pipeline, and the s3_acl option is not explicitly set (defaulting to false). SigV4 presigned URL requests are processed through the S3API middleware and are vulnerable. All RHOSP (13, 16.2, 17.1) and RHOSO (18.0) deployments with s3api enabled in the pipeline are affected. Upstream acknowledges Christian Schwede (NVIDIA) as the original reporter. If S3 API compatibility is not required, remove the s3api filter from the proxy-server pipeline in proxy-server.conf. This completely eliminates the attack surface. If S3 API is required, restrict the distribution and scope of presigned PUT URLs as an operational control, and apply the upstream patch when available. There is no configuration-only workaround that fully mitigates this issue while keeping S3 API functionality enabled. Red Hat OpenStack Platform 13 (Queens) Will not fix rhosp13/openstack-swift-account Red Hat OpenStack Platform 13 (Queens) Will not fix rhosp13/openstack-swift-base Red Hat OpenStack Platform 13 (Queens) Will not fix rhosp13/openstack-swift-container Red Hat OpenStack Platform 13 (Queens) Will not fix rhosp13/openstack-swift-object Red Hat OpenStack Platform 13 (Queens) Will not fix rhosp13/openstack-swift-proxy-server Red Hat OpenStack Platform 16.2 Affected openstack-swift Red Hat OpenStack Platform 16.2 Affected rhosp-rhel8/openstack-swift-account Red Hat OpenStack Platform 16.2 Affected rhosp-rhel8/openstack-swift-base Red Hat OpenStack Platform 16.2 Affected rhosp-rhel8/openstack-swift-container Red Hat OpenStack Platform 16.2 Affected rhosp-rhel8/openstack-swift-object Red Hat OpenStack Platform 16.2 Affected rhosp-rhel8/openstack-swift-proxy-server Red Hat OpenStack Platform 17.1 Affected openstack-swift Red Hat OpenStack Platform 17.1 Affected rhosp-rhel9/openstack-swift-account Red Hat OpenStack Platform 17.1 Affected rhosp-rhel9/openstack-swift-base Red Hat OpenStack Platform 17.1 Affected rhosp-rhel9/openstack-swift-container Red Hat OpenStack Platform 17.1 Affected rhosp-rhel9/openstack-swift-object Red Hat OpenStack Platform 17.1 Affected rhosp-rhel9/openstack-swift-proxy-server Red Hat OpenStack Platform 18.0 Affected openstack-swift Red Hat OpenStack Platform 18.0 Affected rhoso/openstack-swift-account-rhel9 Red Hat OpenStack Platform 18.0 Affected rhoso/openstack-swift-base-rhel9 Red Hat OpenStack Platform 18.0 Affected rhoso/openstack-swift-container-rhel9 Red Hat OpenStack Platform 18.0 Affected rhoso/openstack-swift-object-rhel9 Red Hat OpenStack Platform 18.0 Affected rhoso/openstack-swift-proxy-server-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-71191 https://nvd.nist.gov/vuln/detail/CVE-2026-71191 https://launchpad.net/bugs/2158733