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Potential HTTP policy bypass when using header rules

Low
ferozsalam published GHSA-2h44-x2wx-49f4 May 20, 2023

Package

Cilium

Affected versions

<1.11.16
<1.12.9
<1.13.2

Patched versions

1.11.16
1.12.9
1.13.2

Description

Impact

This issue only impacts users who:

  • Have a HTTP policy that applies to multiple toEndpoints AND
  • Have an allow-all rule in place that affects only one of those endpoints

In such cases, a wildcard rule will be appended to the set of HTTP rules, which could cause bypass of HTTP policies.

Patches

This issue has been patched in Cilium 1.11.16, 1.12.9, and 1.13.2.

Workarounds

Rewrite HTTP rules for each endpoint separately. For example, if the initial rule looks like:

  egress:
    - toEndpoints:
        - matchLabels:
            k8s:kind: echo
        - matchLabels:
            k8s:kind: example
      toPorts:
        - ports:
            - port: "8080"
              protocol: TCP
          rules:
            http:
              - method: "GET"

It should be rewritten to:

  egress:
    - toEndpoints:
        - matchLabels:
            k8s:kind: echo
      toPorts:
        - ports:
            - port: "8080"
              protocol: TCP
          rules:
            http:
              - method: "GET"
    - toEndpoints:
        - matchLabels:
            k8s:kind: example
      toPorts:
        - ports:
            - port: "8080"
              protocol: TCP
          rules:
            http:
              - method: "GET"

Acknowledgements

The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @jrajahalme for investigating and fixing the issue.

For more information

If you have any questions or comments about this advisory, please reach out on Slack.

As usual, if you think you found a related vulnerability, we strongly encourage you to report security vulnerabilities to our private security mailing list: security@cilium.io - first, before disclosing them in any public forums. This is a private mailing list where only members of the Cilium internal security team are subscribed to, and is treated as top priority.

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Adjacent
Attack complexity
High
Privileges required
High
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:A/AC:H/PR:H/UI:N/S:C/C:L/I:N/A:N

CVE ID

CVE-2023-30851

Weaknesses

No CWEs