CVE-2021-20288Network attack vector

Authenticated client impersonation via unchecked global_id reclaim

Published Apr 15, 2021 · Updated Aug 3, 2024

Improper authentication in Ceph allows remote authenticated users to impersonate clients and disrupt cluster services. Ceph monitors fail to validate the old cephx ticket when a reconnecting client reclaims a global_id, permitting reuse of an identifier held by another client. Exploitation requires a valid cluster key, a known or guessed global_id, modified client code, and crafted requests; successful use grants partial impersonation and can interrupt clients or daemons.

CVSS severity7.2
High
EPSS probability2.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Ceph allows remote authenticated users to impersonate clients and disrupt cluster services. Ceph monitors fail to validate the old cephx ticket when a reconnecting client reclaims a global_id, permitting reuse of an identifier held by another client. Exploitation requires a valid cluster key, a known or guessed global_id, modified client code, and crafted requests; successful use grants partial impersonation and can interrupt clients or daemons.

The record

CVE
CVE-2021-20288
Published
Apr 15, 2021
Updated
Aug 3, 2024
Vendor
Ceph
Product
Ceph
Classifications
CWE-287, T1078
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=ceph 14.2.20

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Ceph · Cephversion=ceph 14.2.20

Published CVSS scores

7.2Canonical UbuntuCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
8.0SUSECVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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