Is CVE-2026-39944 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-39944 being exploited in the wild.

How severe is CVE-2026-39944?

High severity, with a CVSS score of 8.8, published 28 August 2026.

Which products and versions are affected?

Ceph prior to 20.2.4 and prior to 19.2.6.

Is there a fix for CVE-2026-39944?

A patch was published on 2026-08-18: Patches released in versions 19.2.6 and 20.2.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-39944 attacked?

It is attacked over the network.

Am I affected by CVE-2026-39944?

Check whether you run Ceph at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-39944: Ceph RADOS Gateway STS token forgery via unauthenticated CBC mode

CVE-2026-39944 · Severity: high · CVSS 8.8 · Published 2026-08-28

Ceph is an open-source distributed storage system that manages large-scale data across multiple servers. The RADOS Gateway (RGW) component, which provides S3-compatible object storage access, uses weak encryption for session tokens. An attacker with any valid token can manipulate it to gain full administrative privileges, potentially accessing or modifying all stored data and administrative settings without needing to break encryption or steal credentials.

Technologies: Ceph. Vendors: Ceph.

Quick answers

Is CVE-2026-39944 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-39944 being exploited in the wild.
How severe is CVE-2026-39944?: High severity, with a CVSS score of 8.8, published 28 August 2026.
Which products and versions are affected?: Ceph prior to 20.2.4 and prior to 19.2.6.
Is there a fix for CVE-2026-39944?: A patch was published on 2026-08-18: Patches released in versions 19.2.6 and 20.2.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-39944 attacked?: It is attacked over the network.
Am I affected by CVE-2026-39944?: Check whether you run Ceph at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is a cryptographic authentication bypass in Ceph's RADOS Gateway STS (Secure Token Service) implementation. RGW encrypts session tokens using AES-128-CBC without message authentication codes (MAC), allowing unauthenticated ciphertext modification. An attacker holding any valid STS token can perform CBC bit-flip attacks to tamper with the acct_type, perm_type, and is_admin fields. Flipping the is_admin bit triggers a global administrative override that bypasses all capability checks. The attack requires only a single valid STS token (which need not be privileged), is remotely exploitable via the S3 endpoint, and requires no encryption oracle or network observation. STS must be enabled and the attacker must have network access to the RGW S3 endpoint. Patches are available in versions 20.2.4 and 19.2.6.

Affected products

Ceph Ceph prior to 20.2.4 and prior to 19.2.6

Timeline

2026-08-28: disclosed
2026-08-18: patched: Patches released in versions 19.2.6 and 20.2.4

References

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