On 2026-08-20 10:32 AM, Iztok Gregori wrote:

Hi!

Silly question maybe, but I want to be sure, for RBD clients (Proxmox QEMU virtual machines in my case) the new key type needs updated "client libraries" to be "understood", right?

Seems to be the case, according to the presentation that talked about the cephx rotation when it was added ( title "Rotating Heads and CephX Keys - Patrick Donnelly, IBM & Yehuda Sadeh Weinraub, Ubiquiti" on youtube; not including link in case it gets blocked. Relevant bit is at 19:50).  Quote from the slide: "Old userspace clients will crash if you attempt to use a new key type!". And while I haven't tested libvirt against 20.2.4 yet, the new key type breaks cephfs mounts on Debian stable (which has ceph-common @ 18.2.7) with an error about parsing the keyring file. -- Pedro Macedo

Cheers Iztok

On 19/08/26 18:07, Patrick Donnelly wrote:

...

Today, August 19th, 2026, the Ceph project has released Tentacle 20.2.4 and Squid 19.2.6 hotfixes for four CVEs across several components.

This is the sixth backport release in the Squid series.

This is the fourth backport release in the Tentacle series.

Additional details will be posted on the Ceph website/blog: https://ceph.io/en/news/blog/

We strongly recommend that all Ceph operators upgrade to one of these releases as soon as possible.

## Critical Upgrade Steps

The fix for CVE-2025-30156 introduces a new CephX key type, aes256k. This is the first time Ceph has introduced a new key type for CephX credentials. Therefore, a new procedure exists for upgrading and rotating Ceph daemon keys as part of this CVE. Before upgrading a Ceph cluster, the operator should familiarize themselves with the procedure documented at:

https://docs.ceph.com/en/latest/rados/configuration/auth-config-ref/index.ht...

These steps are for package-based deployments of Ceph. In other sections, the document also includes new information about key rotation procedures, monitor authentication controls, and emergency recovery procedures.

Deployments using cephadm will automate the process except for client keys. You may notice that Cephadm spends more time than normal on the upgrade after updating all daemon images. This is due to a new process rotating the OSD and MDS keys. Please be patient. There are plans to improve this in the future.

Deployments using Rook will also automate rotation of some client keys with some exclusions. Look to the Rook project’s announcement for more details.

Client and kernel upgrades are recommended to support aes256k. Note that upstream Linux kernel client support began in kernel 7.0 and has been backported to CentOS Stream 9 and 10. Check with your distribution vendor for backported key support before rotating client keys used by the kernel.

As part of upgrading a Ceph cluster, six new health warnings and errors will be generated. This is normal. As part of the process to upgrade/rotate entity keys, you will address the warnings and errors as you go. These are documented beginning here:

https://docs.ceph.com/en/latest/rados/operations/health-checks/index.html#au...

The CephX documentation has been brought up to date and vetted for accuracy. Those changes are live here:

https://docs.ceph.com/en/latest/architecture/index.html#high-availability-au...

Regarding the fix for CVE-2026-54330, RGW will now reject Sigv4 requests with `host` and `x-amz-` headers not included in the signed subset. Unfortunately, the REST client used in multisite was generating such improperly signed requests.

If you are running multisite, you must set the ``rgw_sigv4_insecure`` option to true before you begin to upgrade. After all clusters are upgraded, set the option to ``false`` again.

Regarding the fix for CVE-2026-50152, formal guidance on rotating all secrets stored in the Monitor config-key store will be forthcoming. In the meantime, operators of cephadm-managed clusters are strongly encouraged to rotate the cephadm SSH key, as an established process exists:

See: https://docs.ceph.com/en/latest/cephadm/host-management/#ssh-configuration

Rotating other secrets is advised but the process is not yet established. Operators should assess their cluster's potential exposure to determine if immediate Monitor config-key secret rotation is required for their environment.

## CVE Fixes

* CVE-2025-30156 is an authentication bypass in CephX caused by misuse of AES-CBC.

See: https://docs.ceph.com/en/latest/security/CVE-2025-30156

* CVE-2026-39944 shares the unauthenticated-encryption root cause of CVE-2025-30156, but applies it to RGW's STS session tokens resulting in improper verification of a cryptographic signature.

See: https://docs.ceph.com/en/latest/security/CVE-2026-39944

* CVE-2026-50152 is an improper authorization flaw in the Ceph Monitor subscription handler.

See: https://docs.ceph.com/en/latest/security/CVE-2026-50152

* CVE-2026-54330 is a flaw in RGW not properly verifying its SigV4 cryptographic signatures in RGW's SigV4 verifier.

See: https://docs.ceph.com/en/latest/security/CVE-2026-54330

## Other Media

A Cephalocon 2025 talk covers some of the details surrounding the new CephX key upgrade process.

https://cephalocon2025.sched.com/event/27f2O/rotating-heads-and-cephx-keys-p...

## Getting Ceph ------------ * Source at https://github.com/ceph/ceph * v19.2.6 Tarball at https://download.ceph.com/tarballs/ceph-19.2.6.tar.gz * v20.2.4 Tarball at https://download.ceph.com/tarballs/ceph-20.2.4.tar.gz * Containers at https://quay.io/repository/ceph/ceph * For packages, see https://docs.ceph.com/en/latest/install/get-packages/ * For upgrade with cephadm, see: https://docs.ceph.com/en/latest/cephadm/upgrade/ * v19.2.6 Release git sha1: f9fd95b4335bad6a26d7a74468f55d269e8dbef4 * v20.2.4 Release git sha1: 7f793731f1b39eb4f465e960113d2363c311b964

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