8.1

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

Awaiting analysis
AliasesUBUNTU-CVE-2026-54330USN-8867-1DEBIAN-CVE-2026-54330
Published 27-08-2026Last modified 01-09-2026

Vulnerability summary

CVE-2026-54330 is a high (CVSS 8.1) vulnerability in ceph. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 30.6% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 8.1, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
8.1/10
010
High · v3.1 (CVE.org)
EPSS score
0.37%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2
MGASA-2026-0389RHSA-2026:79101

Timeline

  1. 27-08-2026
    PublishedVulnerability first disclosed.
  2. 01-09-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

31%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.37% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ceph1 product
  • ceph≥ 19.0.0, < 19.2.6 | ≥ 20.0.0, < 20.2.4
Debian1 product
  • cephAll versions (No fix recorded) | < 20.2.4+ds-1
Ubuntu1 product
  • cephAll versions (No fix recorded) | < 12.2.13-0ubuntu0.18.04.11+esm3 | < 15.2.17-0ubuntu0.20.04.6+esm2 | < 17.2.9-0ubuntu0.22.04.4 | < 20.2.0-0ubuntu2.1

3 vendors · 3 products

References

9 links