Description
Ceph is an open-source distributed storage platform providing object, block, and file storage. In versions prior to 20.2.4 and 19.2.6, the Ceph Object Gateway (RGW) SigV4 handler does not reject requests that carry x-amz-* headers absent from the signed header set, allowing anyone holding a presigned URL to attach arbitrary unsigned x-amz-* headers that RGW will honor. AWS S3 requires every x-amz-* header on a SigV4 request to be signed and rejects requests bearing additional unsigned headers, but RGW validates only the headers listed in X-Amz-SignedHeaders and ignores any extra ones, so they take effect without being covered by the signature. By adding such headers to a presigned PUT URL, an attacker can grant themselves more capabilities than the URL's signer intended and escalate their privileges. This issue is fixed in versions 20.2.4 and 19.2.6.
Published: 2026-08-27
Score: 8.1 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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History

Fri, 28 Aug 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 27 Aug 2026 18:00:00 +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. Ceph is an open-source distributed storage platform providing object, block, and file storage. In versions prior to 20.2.4 and 19.2.6, the Ceph Object Gateway (RGW) SigV4 handler does not reject requests that carry x-amz-* headers absent from the signed header set, allowing anyone holding a presigned URL to attach arbitrary unsigned x-amz-* headers that RGW will honor. AWS S3 requires every x-amz-* header on a SigV4 request to be signed and rejects requests bearing additional unsigned headers, but RGW validates only the headers listed in X-Amz-SignedHeaders and ignores any extra ones, so they take effect without being covered by the signature. By adding such headers to a presigned PUT URL, an attacker can grant themselves more capabilities than the URL's signer intended and escalate their privileges. This issue is fixed in versions 20.2.4 and 19.2.6.
Title ceph: ceph: RGW SigV4 verifier allows attachment of arbitrary unsigned x-amz-* headers leading to privilege escalation Ceph RGW SigV4 handler accepts unsigned x-amz-* headers on presigned requests, allowing privilege escalation
References
Metrics 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'}

cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N'}


Fri, 21 Aug 2026 13:30:00 +0000

Type Values Removed Values Added
First Time appeared Ceph
Ceph ceph
Vendors & Products Ceph
Ceph ceph

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


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-08-28T15:57:33.424Z

Reserved: 2026-06-12T18:42:02.224Z

Link: CVE-2026-54330

cve-icon Vulnrichment

Updated: 2026-08-28T15:45:41.151Z

cve-icon NVD

Status : Received

Published: 2026-08-28T00:18:07.683

Modified: 2026-08-28T20:18:16.710

Link: CVE-2026-54330

cve-icon Redhat

Severity : Important

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

Links: CVE-2026-54330 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-28T07:45:04Z

Weaknesses