GHSA-5r23-prx4-mqg3 BIT-cilium-2026-26963 BIT-cilium-operator-2026-26963 BIT-hubble-relay-2026-26963 CVE-2026-26963 GO-2026-4522
Cilium may not enforce host firewall policies when Native Routing, WireGuard and Node Encryption are enabled
- Severity
- 6.1 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.14%
- Chance of exploitation in the next 30 days. Higher than 3.37% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-863 Incorrect Authorization
- Fix
1.18.6- Upgrade github.com/cilium/cilium to this version or later
Description
Impact
Host Policies will incorrectly permit traffic from Pods on other nodes when all of the following configurations are enabled:
These options are disabled by default in Cilium.
Patches
This issue was fixed by #42892.
This issue affects:
- Cilium v1.18 between v1.18.0 and v1.18.5 inclusive
This issue is fixed in:
- Cilium v1.18.6
Workarounds
There is currently no officially verified or comprehensive workaround for this issue. The following procedure has been validated strictly within a local 'Kind' environment and has not undergone exhaustive testing across diverse production architectures. Proceed with caution.
To mitigate the identified traffic bypass, ensure all ingress traffic from the cilium_wg0 interface is explicitly routed to cilium_host for policy enforcement. This ensures that host-level security policies are applied to decrypted WireGuard traffic. Execute the following configuration on each CiliumNode:
# IPv4 Traffic
ip rule add iif cilium_wg0 table 300
ip route add default dev cilium_host table 300
# IPv6 Traffic
ip -6 rule add iif cilium_wg0 table 300
ip -6 route add default dev cilium_net table 300
Acknowledgements
Special thanks to @julianwiedmann for reporting the issue and helping with the resolution.
For more information
If you think you have found a vulnerability affecting Cilium, we strongly encourage you to report it to our security mailing list at security@cilium.io. This is a private mailing list for the Cilium security team, and your report will be treated as top priority. Please also address any comments or questions on this advisory to the same mailing list.
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| github.com/cilium/cilium | >= 1.18.0, < 1.18.6 |
1.18.6 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
github.com/cilium/cilium Go → 1.18.6
- go
go get github.com/cilium/cilium@v1.18.6 && go mod tidy
Severity breakdown
CVSS 3.1 6.1
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- Attack vector
- Adjacent
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Weakness
CWE-863: Incorrect Authorization
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
How to prevent it
- Architecture and Design: Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Architecture and Design: Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor [REF-7].
- Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
- Architecture and Design: For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page. One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
- System Configuration, Installation: Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-fm8w-2m5w-9j7r Cilium may unexpectedly allow ingress traffic from the local namespace when a Kubernetes NetworkPolicy is configured with an ipBlock match | Medium | Also affects github.com/cilium/cilium |
| GHSA-w7c2-w76w-5hmj Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces | High | Also affects github.com/cilium/cilium |
| GHSA-q6h5-q3q6-f87x CiliumLocalRedirectPolicy addressMatcher allows cross-namespace service traffic hijacking and can break service translation | Medium | Also affects github.com/cilium/cilium |
| GHSA-3fcv-jvfp-m4q9 Cilium vulnerable to sensitive information disclosure and cluster disruption via local Envoy admin socket access | High | Also affects github.com/cilium/cilium |
| GHSA-gj49-89wh-h4gj Cillium exposes sensitive information included in the cilium-bugtool debug archive | Medium | Also affects github.com/cilium/cilium |
| GHSA-hxv8-4j4r-cqgv Cilium L7 proxy may bypass Kubernetes NetworkPolicy for same-node traffic | Medium | Also affects github.com/cilium/cilium |
| GHSA-38pp-6gcp-rqvm Cilium with misconfigured toGroups in policies can lead to unrestricted egress traffic | Medium | Also affects github.com/cilium/cilium |
| GHSA-5vxx-c285-pcq4 In Cilium, packets from terminating endpoints may not be encrypted in Wireguard-enabled clusters | Medium | Also affects github.com/cilium/cilium |
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