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Cilium with misconfigured toGroups in policies can lead to unrestricted egress traffic

Moderate severity GitHub Reviewed Published Nov 27, 2025 in cilium/cilium • Updated Dec 1, 2025

Package

gomod Ciliumgithub.com/cilium/cilium (Go)

Affected versions

>= 1.17.0, < 1.17.10

Patched versions

1.17.10
gomod github.com/cilium/cilium (Go)
>= 1.18.0, < 1.18.4
< 1.16.17
1.18.4
1.16.17

Description

Impact

CiliumNetworkPolicys which use egress.toGroups.aws.securityGroupsIds to reference AWS security group IDs that do not exist or are not attached to any network interface may unintentionally allow broader outbound access than intended by the policy authors. In such cases, the toCIDRset section of the derived policy is not generated, which means outbound traffic may be permitted to more destinations than originally intended.

Patches

This issue has been patched in:

  • Cilium v1.18.4
  • Cilium v1.17.10
  • Cilium v1.16.17

This issue affects:

  • Cilium v1.18 between v1.18.0 and v1.18.3 inclusive
  • Cilium v1.17 between v1.17.0 and v1.17.9 inclusive
  • Cilium v1.16.16 and below

Workarounds

There is no workaround to this issue.

Acknowledgements

The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @SeanEmac for reporting this issue and to @fristonio for the patch.

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 [email protected]. This is a private mailing list for the Cilium security team, and your report will be treated as top priority.

References

@ferozsalam ferozsalam published to cilium/cilium Nov 27, 2025
Published by the National Vulnerability Database Nov 29, 2025
Published to the GitHub Advisory Database Dec 1, 2025
Reviewed Dec 1, 2025
Last updated Dec 1, 2025

Severity

Moderate

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
Local
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
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:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(2nd percentile)

Weaknesses

Improper Access Control

The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Learn more on MITRE.

CVE ID

CVE-2025-64715

GHSA ID

GHSA-38pp-6gcp-rqvm

Source code

Credits

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