CVE-2026-39944Network attack vectorHinoki check available

Administrative privilege escalation via STS token bit-flipping

Published Aug 27, 2026 · Updated Aug 27, 2026

Privilege escalation in Ceph RGW before 19.2.6 and before 20.2.4 allows remote authenticated users to gain full RGW administration. The STS token handler encrypts acct_type and is_admin with unauthenticated AES-128-CBC, so ciphertext bit flips alter those fields without detection. STS must be enabled, and a valid unprivileged token is required; a forged is_admin value bypasses capability checks and permits reading, writing, or deleting all RGW objects and buckets.

CVSS severity8.5
High
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Privilege escalation in Ceph RGW before 19.2.6 and before 20.2.4 allows remote authenticated users to gain full RGW administration. The STS token handler encrypts acct_type and is_admin with unauthenticated AES-128-CBC, so ciphertext bit flips alter those fields without detection. STS must be enabled, and a valid unprivileged token is required; a forged is_admin value bypasses capability checks and permits reading, writing, or deleting all RGW objects and buckets.

The record

CVE
CVE-2026-39944
Published
Aug 27, 2026
Updated
Aug 27, 2026
Vendor
Ceph
Product
Ceph
Classifications
CWE-327, T1134
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2026Record 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=>= 19.0.0, < 19.2.6
  2. Affected versionversion=>= 20.0.0, < 20.2.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Ceph · Cephversion=>= 19.0.0, < 19.2.6; version=>= 20.0.0, < 20.2.4

Published CVSS scores

8.5Red HatCVSS:3.1/AV:N/AC:H/PR:L/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-327Use of a Broken or Risky Cryptographic Algorithm
T1134Access Token Manipulation

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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