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Date: Tue, 5 Oct 2021 19:06:50 +0200
From: Richard Hartmann <richih.mailinglist@...il.com>
To: oss-security@...ts.openwall.com
Subject: CVE-2021-39226 Grafana snapshot authentication bypass
Today we are releasing Grafana 7.5.11, and 8.1.6. These patch releases
include an important security fix for an issue that affects all
Grafana versions from 2.0.1.
[Grafana Cloud](https://grafana.com/cloud) instances have already been
patched and an audit did not find any usage of this attack vector.
[Grafana Enterprise](https://grafana.com/products/enterprise)
customers were provided with updated binaries under embargo.
8.1.5 contained a single fix for bar chart panels. We believe that
users can expedite deployment by moving from 8.1.4 to 8.1.6 directly.
## CVE-2021-39226 Snapshot authentication bypass
### Summary
CVSS Score: 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
We received a security report to
[security@...fana.com](mailto:security@...fana.com) on 2021-09-15
about a vulnerability in Grafana regarding the snapshot feature. It
was later identified as affecting Grafana versions from 2.0.1 to
8.1.6. [CVE-2021-39226](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39226)
has been assigned to this vulnerability.
### Impact
Unauthenticated and authenticated users are able to view the snapshot
with the lowest database key by accessing the literal paths:
* `/dashboard/snapshot/:key`, or
* `/api/snapshots/:key`
If the snapshot "public_mode" configuration setting is set to true (vs
default of false), unauthenticated users are able to delete the
snapshot with the lowest database key by accessing the literal path:
* `/api/snapshots-delete/:deleteKey`
Regardless of the snapshot "public_mode" setting, authenticated users
are able to delete the snapshot with the lowest database key by
accessing the literal paths:
* `/api/snapshots/:key`, or
* `/api/snapshots-delete/:deleteKey`
The combination of deletion and viewing enables a complete walk
through all snapshot data while resulting in complete snapshot data
loss.
### Attack audit
While we can not guarantee that the below will identify all attacks,
if you do find something with the below, you should consider doing a
full assessment.
#### Through reverse proxy/load balancer logs
To determine if your Grafana installation has been exploited for this
vulnerability, search through your reverse proxy/load balancer access
logs for instances where the path is `/dashboard/snapshot/:key`,
`/api/snapshots/:key` or `/api/snapshots-delete/:deleteKey`, and the
response status code was 200 (OK).
For example, if you’re using the Kubernetes ingress-nginx controller
and sending logs to Loki, use a LogQL query like
`{job="nginx-ingress-controller"} |= "\"status\": 200" |= "\"uri\":
\"/api/snapshots/:key\""`.
#### Through the Grafana Enterprise audit feature
If you enabled “Log web requests” in your configuration with
`router_logging = true`, look for
`"requestUri":"/api/snapshots-delete/”`,`“requestUri":"/api/snapshots/:key"`,
or `"type":"snapshot"` in combination with `"action":"delete"`.
### Patched versions
Release 8.1.6:
- [Download Grafana 8.1.6](https://grafana.com/grafana/download/8.1.6)
- [Release notes](https://grafana.com/docs/grafana/latest/release-notes/release-notes-8-1-6/)
Release 7.5.11:
- [Download Grafana 7.5.11](https://grafana.com/grafana/download/7.5.11)
- [Release notes](https://grafana.com/docs/grafana/latest/release-notes/release-notes-7-5-11/)
### Solutions and mitigations
Download and install the appropriate patch for your version of Grafana.
[Grafana Cloud](https://grafana.com/cloud) instances have already been
patched, and [Grafana
Enterprise](https://grafana.com/products/enterprise) customers were
provided with updated binaries under embargo.
### Workaround
If for some reason you cannot upgrade:
You can use a reverse proxy or similar to block access to the literal paths
* `/api/snapshots/:key`
* `/api/snapshots-delete/:deleteKey`
* `/dashboard/snapshot/:key`
* `/api/snapshots/:key`
They have no normal function and can be disabled without side effects.
### Timeline and postmortem
Here is a detailed timeline starting from when we originally learned
of the issue. All times in UTC.
* 2021-09-15 14:49: Tuan Tran theblackturtle0901@...il.com sends
initial report about viewing snapshots without authentication
* 2021-09-15 15:56: Initial reproduction
* 2021-09-15 17:10: MEDIUM severity declared
* 2021-09-15 18:58: Workaround deployed on Grafana Cloud
* 2021-09-15 19:15: `/api/snapshots/:key` found to be vulnerable as well
* 2021-09-15 19:30: `/api/snapshots/:key` blocked on Grafana Cloud
* 2021-09-16 09:31: `/api/snapshots-delete/:deleteKey` found to be
vulnerable as well, blocked on Grafana Cloud. From this point forward,
Cloud is not affected any more.
* 2021-09-16 09:35: HIGH severity declared
* 2021-09-16 11:19: Realization that combination of deletion and
viewing allows enumeration and permanent DoS
* 2021-09-16 11:19: CRITICAL declared
* 2021-09-17 10:53: Determination that no weekend work is needed.
While issue is CRITICAL, scope is very limited
* 2021-09-17 14:26: Audit of Grafana Cloud concluded, no evidence of
exploitation
* 2021-09-23: Grafana Cloud instances updated
* 2021-09-28 12:00: Grafana Enterprise images released to customers
under embargo
* 2021-10-05: Public release
## Reporting security issues
If you think you have found a security vulnerability, please send a
report to [security@...fana.com](mailto:security@...fana.com). This
address can be used for all of
Grafana Labs's open source and commercial products (including but not
limited to Grafana, Tempo, Loki, Amixr, k6, Tanka, and Grafana Cloud,
Grafana Enterprise, and grafana.com). We only accept vulnerability
reports at this address. We would prefer that you encrypt your message
to us using our PGP key. The key fingerprint is:
F988 7BEA 027A 049F AE8E 5CAA D125 8932 BE24 C5CA
The key is available from
[keys.gnupg.net](http://keys.gnupg.net/pks/lookup?op=get&fingerprint=on&search=0xD1258932BE24C5CA)
by searching for
[security@...fana](http://keys.gnupg.net/pks/lookup?search=security@grafana&fingerprint=on&op=index.
## Security announcements
We maintain a category on the community site named [Security
Announcements](https://community.grafana.com/c/security-announcements),
where we will post a summary, remediation, and mitigation details for
any patch containing security fixes. You can also subscribe to email
updates to this category if you have a grafana.com account and sign in
to the community site, or via updates from our [Security Announcements
RSS feed](https://community.grafana.com/c/security-announcements.rss).
## Acknowledgement
We would like to thank [Tran Viet
Tuan](https://github.com/theblackturtle) for responsibly disclosing
the initially discovered vulnerability to us.
Best,
Richard
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