CVE-2022-21951 — rancher
MEDIUMCVE-2022-21951 is a medium-severity (CVSS 6.8) CWE-319 vulnerability in github.com/rancher/rancher. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/rancher/rancher — see the affected versions and patch details below.
Rancher: Weave CNI password is not set if RKE template is used with CNI value overridden
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2022-21951 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/rancher/rancher🐹github.com/rancher/rancherReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
This vulnerability only affects customers using Weave CNI (Container Network Interface) when configured through RKE templates.
A flaw was discovered in Rancher versions from 2.5.0 up to and including 2.5.13 and from 2.6.0 up to and including 2.6.4, where a UI (user interface) issue with RKE templates does not include a value for the Weave password when Weave is chosen as the CNI.
If a cluster is created based on the mentioned template and Weave is configured as the CNI, no password will be created for network encryption in Weave, therefore network traffic in the cluster will be sent unencrypted.
This issue does not happen when a cluster, with Weave configured as CNI, is created without using an RKE template.
The impact of this vulnerability is higher when nodes on the cluster are on different locations and communicate with one another through the Internet, where monitoring (sniffing) of the network traffic by third-party entities can be more easily achieved.
Patches
Patched versions include releases 2.5.14, 2.6.5 and later versions of Rancher. Besides upgrading to a Rancher patched version, the workarounds listed below must be applied in order for Weave to properly encrypt the network traffic.
Workarounds
- A manual password can be set in Weave by directly editing Weave's DaemonSet on the affected cluster to add the
WEAVE_PASSWORDenvironment variable together with the a value for the password.
$ kubectl -n kube-system edit ds weave-net
<snipped>
containers:
- command:
- /home/weave/launch.sh
env:
- name: INIT_CONTAINER
value: "true"
- name: HOSTNAME
valueFrom:
fieldRef:
apiVersion: v1
fieldPath: spec.nodeName
- name: IPALLOC_RANGE
value: <IP allocation range>
- name: WEAVE_PASSWORD
value: "insert strong secret password here"
image: <Weave image>
<snipped>
- A new RKE template revision must be created in order to properly generate the Weave password on new clusters.
Notes
-
In order to provide protection against brute-force attacks, that might break the network encryption, a strong password must be generated for the workaround. Weave's documentation provides recommendations for generating a strong password.
-
Manually generating the password for the workaround is only needed on affected versions of Rancher. This step is not needed when creating new RKE templates on patched versions of Rancher.
For more information
If you have any questions or comments about this advisory:
- Reach out to SUSE Rancher Security team for security related inquiries.
- Open an issue in Rancher repository.
- Verify SUSE Rancher support matrix and product support lifecycle.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/rancher/rancher | ≥ 2.6.0&&< 2.6.5 | 2.6.5go get github.com/rancher/rancher@v2.6.5 |
| 🐹Go | github.com/rancher/rancher | ≥ 2.5.0&&< 2.5.14 | 2.5.14go get github.com/rancher/rancher@v2.5.14 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/rancher/rancher, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/rancher/rancher to 2.6.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-21951 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2022-21951 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2022-21951. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2022-21951 in your dependencies?
O3 Security finds CVE-2022-21951 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.