A flaw was found in Ceph RGW's SigV4 signature verification handler. When processing S3 requests, RGW verifies only the headers explicitly listed in the X-Amz-SignedHeaders field but does not reject requests that carry additional unsigned x-amz-* headers. This diverges from the AWS S3 specification, which requires all x-amz-* headers to be signed. As a result, anyone holding a presigned PUT URL can attach arbitrary unsigned x-amz-* headers that RGW will honor, effectively escalating their privileges beyond what the original URL signer authorized. This can lead to unauthorized access to and modification of S3 objects.

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History

Thu, 20 Aug 2026 00:15:00 +0000

Type Values Removed Values Added
Description A flaw was found in Ceph RGW's SigV4 signature verification handler. When processing S3 requests, RGW verifies only the headers explicitly listed in the X-Amz-SignedHeaders field but does not reject requests that carry additional unsigned x-amz-* headers. This diverges from the AWS S3 specification, which requires all x-amz-* headers to be signed. As a result, anyone holding a presigned PUT URL can attach arbitrary unsigned x-amz-* headers that RGW will honor, effectively escalating their privileges beyond what the original URL signer authorized. This can lead to unauthorized access to and modification of S3 objects.
Title ceph: ceph: RGW SigV4 verifier allows attachment of arbitrary unsigned x-amz-* headers leading to privilege escalation
Weaknesses CWE-347
References
Metrics threat_severity

None

cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N'}

threat_severity

Important


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cve-icon MITRE

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cve-icon Vulnrichment

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cve-icon NVD

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cve-icon Redhat

Severity : Important

Publid Date: 2026-08-19T17:57:46Z

Links: CVE-2026-54330 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-20T08:15:17Z

Weaknesses