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Date: Wed, 10 May 2023 17:21:01 +0000
From: Jeremy Stanley <>
Subject: [OSSA-2023-003] cinder, glance_store, nova, os-brick: Unauthorized
 volume access through deleted volume attachments (CVE-2023-2088)

OSSA-2023-003: Unauthorized volume access through deleted volume attachments

:Date: May 10, 2023
:CVE: CVE-2023-2088

- Cinder: <20.2.1, >=21.0.0 <21.2.1, ==22.0.0
- Glance_store: <3.0.1, >=4.0.0 <4.1.1, >=4.2.0 <4.3.1
- Nova: <25.1.2, >=26.0.0 <26.1.2, ==27.0.0
- Os-brick: <5.2.3, >=6.0.0 <6.1.1, >=6.2.0 <6.2.2

An unauthorized access to a volume could occur when an iSCSI or FC
connection from a host is severed due to a volume being unmapped on
the storage system and the device is later reused for another volume
on the same host.

**Scope:** Only deployments with iSCSI or FC volumes are affected.
However, the fix for this issue includes a configuration change in
Nova and Cinder that may impact you on your next upgrade regardless
of what backend storage technology you use. See the *Configuration
change* section below, and item 4(B) in the *Patches and Associated
Deployment Changes* for details.

This data leak can be triggered by two different situations.

**Accidental case:** If there is a problem with network connectivity
during a normal detach operation, OpenStack may fail to clean the
situation up properly. Instead of force-detaching the compute node
device, Nova ignores the error, assuming the instance has already
been deleted. Due to this incomplete operation OpenStack may end up
selecting the wrong multipath device when connecting another volume
to an instance.

**Intentional case:** A regular user can create an instance with a
volume, and then delete the volume attachment directly in Cinder,
which neglects to notify Nova. The compute node SCSI plumbing (over
iSCSI/FC) will continue trying to connect to the original
host/port/LUN, not knowing the attachment has been deleted. If a
subsequent volume attachment re-uses the host/port/LUN for a
different instance and volume, the original instance will gain
access to it once the SCSI plumbing reconnects.

Configuration Change
To prevent the intentional case, the Block Storage API provided by
Cinder must only accept attachment delete requests from Nova for
instance-attached volumes. A complicating factor is that Nova
deletes an attachment by making a call to the Block Storage API on
behalf of the user (that is, by passing the user's token), which
makes the request indistinguishable from the user making this
request directly. The solution is to have Nova include a service
token along with the user's token so that Cinder can determine that
the detach request is coming from Nova. The ability for Nova to pass
a service token has been supported since Ocata, but has not been
required until now. Thus, deployments that are not currently sending
service user credentials from Nova will need to apply the relevant
code changes and also make configuration changes to solve the

Patches and Associated Deployment Changes
Given the above analysis, a thorough fix must include the following

1. The os-brick library must implement the ``force`` option for
   fibre channel, which which has only been available for iSCSI
   until now (covered by the linked patches).

2. Nova must call os-brick with the ``force`` option when
   disconnecting volumes from deleted instances (covered by the
   linked patches).

3. In deployments where Glance uses the cinder glance_store driver,
   glance must call os-brick with the ``force`` option when
   disconnecting volumes (covered by the linked patches).

4. Cinder must distinguish between safe and unsafe attachment delete
   requests and reject the unsafe ones. This part of the fix has two

   a. The Block Storage API will return a 409 (Conflict) for a
      request to delete an attachment if there is an instance
      currently using the attachment, **unless** the request is
      being made by a service (for example, Nova) on behalf of a
      user (covered by the linked patches).

   b. In order to recognize that a request is being made by a
      service on behalf of a user, Nova must be configured to send a
      service token along with the user token. If this configuration
      change is not made, the cinder change will reject **any**
      request to delete an attachment associated with a volume that
      is attached to an instance. Nova must be configured to send a
      service token to Cinder, and Cinder must be configured to
      accept service tokens. This is described in the following
      PATCHES:** (Using service tokens to prevent long-running job
      The Nova patch mentioned in step 2 includes a similar document
      more focused on Nova:

5. The cinder glance_store driver does not attach volumes to
   instances; instead, it attaches volumes directly to the Glance
   node. Thus, the Cinder change in step 4 will recognize an
   attachment-delete request coming from Glance as safe and allow
   it. (Of course, we expect that you will have applied the patches
   in steps 1 and 3 to your Glance nodes.)

An additional nova patch is required to fix a minor regression in periodic tasks and some nova-manage actions (errata 1). Also a patch to tempest is needed to account for behavior changes with fixes in place (errata 2).

- (2023.1/antelope cinder)
- (2023.1/antelope glance_store)
- (2023.1/antelope nova)
- (2023.1/antelope nova errata 1)
- (2023.1/antelope os-brick)
- (2023.2/bobcat cinder)
- (2023.2/bobcat glance_store)
- (2023.2/bobcat nova)
- (2023.2/bobcat nova errata 1)
- (2023.2/bobcat os-brick)
- (2023.2/bobcat tempest errata 2)
- (Wallaby nova)
- (Wallaby nova errata 1)
- (Xena cinder)
- (Xena glance_store)
- (Xena nova)
- (Xena nova errata 1)
- (Xena os-brick)
- (Yoga cinder)
- (Yoga glance_store)
- (Yoga nova)
- (Yoga nova errata 1)
- (Yoga os-brick)
- (Zed cinder)
- (Zed glance_store)
- (Zed nova)
- (Zed nova errata 1)
- (Zed os-brick)

- Jan Wasilewski from Atman (CVE-2023-2088)
- Gorka Eguileor from Red Hat (CVE-2023-2088)


- Limited Protection Against Accidents... If you are only concerned with
  protecting against the accidental case described earlier in this document,
  steps 1-3 above should be sufficient. Note, however, that only applying steps
  1-3 leaves your cloud wide open to the intentional exploitation of this
  vulnerability. Therefore, we recommend that the full fix be applied to all
- Using Configuration as a Short-Term Mitigation... An alternative approach to
  mitigation can be found in OSSN-0092
- The stable/xena and stable/wallaby branches are under extended maintenance
  and will receive no new point releases, but patches for them are provided as
  a courtesy where available.

OSSA History
- 2023-05-10 - Errata 2
- 2023-05-10 - Errata 1
- 2023-05-10 - Original Version

Jeremy Stanley
OpenStack Vulnerability Management Team

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