CVE-2026-53935: Github.com/cilium/cilium CiliumLocalRedirectPolicy AddressMatcher Allows Cross-namespace Service Vulnerability

MODERATE
Advisory Identifier: GHSA-q6h5-q3q6-f87x
Share
CVSS 6.9
CWE-601
Published
Advisory Summary

CVE-2026-53935 is a MODERATE (CVSS 6.9) ciliumlocalredirectpolicy addressmatcher allows cross-namespace service vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Github.com/cilium/cilium libraries in the Go ecosystem. The issue involves ciliumlocalredirectpolicy addressmatcher allows cross-namespace service traffic hijacking and can break service translation. Remediation is available by upgrading affected packages to version 1.19.4, 1.18.10, 1.17.16.

CVE-2026-53935 at a Glance

CVE Identifier CVE-2026-53935
GHSA Identifier GHSA-q6h5-q3q6-f87x
Severity MODERATE
CVSS v3.1 Base Score 6.9
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Github.com/cilium/cilium
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 6.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:L/I:N/A:H).

Attack Vector Adjacent (AV:A)
Attack Complexity Low (AC:L)
Privileges Required High (PR:H)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-53935

To remediate this vulnerability, upgrade all affected Github.com/cilium/cilium dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/cilium/cilium fixed: 1.19.4 
Upgrade github.com/cilium/cilium to 1.19.4
github.com/cilium/cilium fixed: 1.18.10 
Upgrade github.com/cilium/cilium to 1.18.10
github.com/cilium/cilium fixed: 1.17.16 
Upgrade github.com/cilium/cilium to 1.17.16
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/cilium/cilium

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-53935, inspect your project dependencies for Github.com/cilium/cilium:

inspect dependencies for github.com/cilium/cilium

Analyze the terminal output to locate any version of Github.com/cilium/cilium in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.19.4), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Github.com/cilium/cilium, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Users with the ability to create CiliumLocalRedirectPolicies can specify arbitrary ClusterIPs via addressMatcher, which enables hijacking traffic to Services in any namespace, bypassing the namespace-scoping guarantees enforced by serviceMatcher. In addition, deleting such a policy can corrupt Cilium's internal service state, causing service translation to stop working entirely for the affected Service. ### Patches This issue affects: - Cilium v1.19.0 to v1.19.3 inclusive (fixed in PR #45584) - Cilium v1.18.2 to v1.18.9 inclusive (fixed in PR #45585) - All versions of Cilium prior to v1.17.16 (fixed in PR #45412) This issue has been patched in: - Cilium v1.19.4 - Cilium v1.18.10 - Cilium v1.17.16 ### 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 @ysksuzuki for investigating and fixing the issue. ### For more information If there are any questions or comments about this advisory, please reach out on [Slack](https://docs.cilium.io/en/latest/community/community/). To report potential vulnerabilities affecting Cilium, it strongly is encouraged to report them through the security mailing list at [security@cilium.io](mailto:security@cilium.io). This is a private mailing list for the Cilium security team, and reports will be treated as a top priority.

CVE-2026-53935 Affected Github.com/cilium/cilium Versions

3 component(s)
Fixed Versions:
1.19.41.18.101.17.16
Product / Package Ecosystem Affected Versions Fixed Version
github.com/cilium/cilium
golang/github.com/cilium/cilium
Go
≥ 1.19.0
< 1.19.4
1.19.4
github.com/cilium/cilium
golang/github.com/cilium/cilium
Go
≥ 1.18.2
< 1.18.10
1.18.10
github.com/cilium/cilium
golang/github.com/cilium/cilium
Go
< 1.17.16
1.17.16

References

GitHub Advisory / Wiki ADVISORY
https://github.com/cilium/cilium/security/advisories/GHSA-q6h5-q3q6-f87x
Github.com/cilium/cilium Source Repository REPOSITORY
https://github.com/cilium/cilium/pull/44512
Github.com/cilium/cilium Source Repository REPOSITORY
https://github.com/cilium/cilium/pull/44584
Github.com/cilium/cilium Source Repository REPOSITORY
https://github.com/cilium/cilium/pull/44585
Github.com/cilium/cilium Source Repository REPOSITORY
https://github.com/cilium/cilium

Frequently Asked Questions

What is CVE-2026-53935?
CVE-2026-53935 is a security vulnerability in Github.com/cilium/cilium involving CiliumLocalRedirectPolicy addressMatcher allows cross-namespace service traffic hijacking and can break service translation under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Github.com/cilium/cilium versions are affected?
Affected versions include releases prior to 1.19.4, 1.18.10, 1.17.16 across affected packages: github.com/cilium/cilium.
What version fixes CVE-2026-53935?
Upgrading to 1.19.4, 1.18.10, 1.17.16 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/cilium/cilium affected?
Yes, github.com/cilium/cilium is affected in releases prior to 1.19.4, 1.18.10, 1.17.16. Upgrade your dependency to 1.19.4, 1.18.10, 1.17.16 or later.
What is the CVSS score of CVE-2026-53935?
CVE-2026-53935 has a CVSS v3.1 base score of 6.9 (MODERATE) with vector string CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:L/I:N/A:H.
What CWE is associated with CVE-2026-53935?
CVE-2026-53935 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check Go dependencies for CVE-2026-53935?
Run the dependency tree command: 'inspect dependencies for github.com/cilium/cilium'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-q6h5-q3q6-f87x",
  "modified" : "2026-07-06T20:45:38Z",
  "published" : "2026-07-06T20:45:38Z",
  "aliases" : [ "CVE-2026-53935" ],
  "summary" : "CiliumLocalRedirectPolicy addressMatcher allows cross-namespace service traffic hijacking and can break service translation",
  "details" : "### Impact\n\nUsers with the ability to create CiliumLocalRedirectPolicies can specify arbitrary ClusterIPs via addressMatcher, which enables hijacking traffic to Services in any namespace, bypassing the namespace-scoping guarantees enforced by serviceMatcher.\n\nIn addition, deleting such a policy can corrupt Cilium's internal service state, causing service translation to stop working entirely for the affected Service.\n\n### Patches\n\nThis issue affects:\n\n- Cilium v1.19.0 to v1.19.3 inclusive  (fixed in PR #45584)\n- Cilium v1.18.2 to v1.18.9 inclusive (fixed in PR #45585)\n- All versions of Cilium prior to v1.17.16 (fixed in PR #45412)\n\nThis issue has been patched in:\n\n- Cilium v1.19.4\n- Cilium v1.18.10\n- Cilium v1.17.16\n\n### Workarounds\n\nThere is no workaround to this issue.\n\n### Acknowledgements\n\nThe Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @ysksuzuki for investigating and fixing the issue.\n\n### For more information\nIf there are any questions or comments about this advisory, please reach out on [Slack](https://docs.cilium.io/en/latest/community/community/).\n\nTo report potential vulnerabilities affecting Cilium, it strongly is encouraged to report them through the security mailing list at [security@cilium.io](mailto:security@cilium.io). This is a private mailing list for the Cilium security team, and reports will be treated as a top priority.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:L/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cilium/cilium"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.19.0"
      }, {
        "fixed" : "1.19.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cilium/cilium"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.18.2"
      }, {
        "fixed" : "1.18.10"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cilium/cilium"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.17.16"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/security/advisories/GHSA-q6h5-q3q6-f87x"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/pull/44512"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/pull/44584"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/pull/44585"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/cilium/cilium"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-06T20:45:38Z",
    "nvd_published_at" : null
  }
}