CVE-2026-54330: Ceph RGW SigV4 handler accepts unsigned x-amz-* headers on presigned requests, allowing privilege escalation

highCVSS 8.1CVE-2026-54330

CSIRTS triage

vendor: Ceph product: Ceph RGW Authentication bypass Privilege escalation

What: Ceph RGW SigV4 handler accepts unsigned x-amz-* headers on presigned requests, enabling privilege escalation.
Who is affected: Ceph RGW deployments using SigV4 authentication are affected.
Urgency: High severity (CVSS 8.1) allows privilege escalation via unsigned headers; immediate patching required.
Action: Apply Ceph security patches addressing SigV4 header validation.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 8.1
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54330

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-543300.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-54330	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Ceph RGW SigV4

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-54330: Ceph is an open-source distributed storage platform providing object, block, and file storage.…nvd · 2026-08-28