CVE-2026-71192 in Swift
Summary
by MITRE • 08/05/2026
In OpenStack Swift through 2.38.0, the S3API middleware does not sanitize Swift-native control headers (X-Copy-From, X-Copy-From-Account) from S3 API requests when s3_acl=true. An attacker can inject these headers into a signed PUT request targeting their own bucket, causing Swift to perform a server-side copy from another tenant's private object. The source object authorization is bypassed because the S3API middleware has already authorized the request against the destination. The attacker can read any object whose project_id, container name, and object name are known, regardless of the source object's ACLs or ownership. This requires the non-default s3_acl=true configuration.
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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability in OpenStack Swift versions through 2.38.0 represents a critical access control flaw within the S3API middleware implementation that enables unauthorized cross-tenant data access through server-side copy operations. This issue specifically affects deployments where the s3_acl=true configuration is enabled, creating a dangerous condition where control headers intended for internal Swift operations become weaponized by attackers. The vulnerability stems from insufficient input sanitization within the S3 compatibility layer, allowing malicious actors to inject Swift-native control headers such as X-Copy-From and X-Copy-From-Account into legitimate signed PUT requests.
The technical mechanism of exploitation relies on the middleware's failure to properly validate and sanitize control headers before processing S3 API requests. When s3_acl=true is configured, the S3API middleware performs initial authorization against the destination resource but fails to strip or validate Swift-specific control headers that should not be present in S3 API calls. This creates a scenario where an authenticated user can manipulate their request to include these control headers, effectively bypassing the normal authorization flow that would normally prevent access to objects owned by different tenants. The vulnerability operates at the intersection of several CWE categories including CWE-20 for improper input validation and CWE-284 for improper access control, with implications that align with ATT&CK technique T1078 for valid accounts and T1566 for social engineering through API misuse.
The operational impact of this vulnerability extends far beyond simple data theft, as it enables comprehensive cross-tenant data exfiltration without detection. An attacker with knowledge of a target's project_id, container name, and object name can leverage this flaw to access any private object from other tenants within the same Swift deployment, regardless of the source object's access control lists or ownership permissions. This represents a fundamental breakdown in multi-tenancy isolation, potentially exposing sensitive customer data, configuration information, or business-critical assets across different project boundaries. The vulnerability is particularly concerning because it requires only knowledge of target resource identifiers rather than direct authentication credentials for those resources, making it exploitable through reconnaissance alone.
Mitigation strategies must address both the immediate configuration risks and implement broader security controls to prevent such cross-tenant access patterns. Organizations should immediately disable s3_acl=true unless absolutely required for business operations, as this configuration is explicitly mentioned as necessary for the vulnerability to exist. Additionally, implementing strict header validation policies within the S3API middleware layer would prevent unauthorized control header injection, ensuring that Swift-native headers are only processed in appropriate contexts. Network-level controls such as firewall rules and API gateway restrictions can also help limit exposure by preventing unauthorized access patterns, while comprehensive logging and monitoring should track unusual cross-tenant access attempts. The implementation of proper input sanitization and validation procedures aligns with security best practices outlined in NIST SP 800-53 and ISO 27001 controls for access control management, ensuring that such vulnerabilities are prevented through defensive programming techniques and proper configuration management.