How severe is CVE-2026-53935?

CVE-2026-53935 has a CVSS score of 6.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-53935?

CVE-2026-53935 affects the following packages: github.com/cilium/cilium (Go), github.com/cilium/cilium (Go), github.com/cilium/cilium (Go). Ecosystems affected: Go.

How do I fix CVE-2026-53935?

Update github.com/cilium/cilium to 1.19.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53935 is resolved across your whole dependency graph.

How do I detect CVE-2026-53935 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cilium/cilium, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-53935 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-53935 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-53935 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-53935?

CVE-2026-53935 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 26th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-53935?

CVE-2026-53935 is classified as CWE-863 (CWE-863). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-53935 published, and has it been updated?

CVE-2026-53935 was published on July 7, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

MEDIUM severity

CVE-2026-53935 — cilium

MEDIUMFix: cilium/cilium@81d4463

CVE-2026-53935 is a medium-severity (CVSS 6.9) CWE-863 vulnerability in github.com/cilium/cilium. A fix is available for github.com/cilium/cilium — see the affected versions and patch details below.

CiliumLocalRedirectPolicy addressMatcher allows cross-namespace service traffic hijacking and can break service translation

Also known asBIT-cilium-2026-53935BIT-cilium-operator-2026-53935BIT-hubble-relay-2026-53935GHSA-q6h5-q3q6-f87xGO-2026-5914

Published

Jul 7, 2026

Updated

Oct 21, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Oct 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-53935.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs26th percentile — riskier than 26% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-53935 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

3 pkgs affected

🐹github.com/cilium/cilium🐹github.com/cilium/cilium🐹github.com/cilium/cilium

Real-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

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.

To report potential vulnerabilities affecting Cilium, it strongly is encouraged to report them through the security mailing list at [email protected]. This is a private mailing list for the Cilium security team, and reports will be treated as a top priority.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/cilium/cilium`	≥ 1.19.0&&< 1.19.4	1.19.4`go get github.com/cilium/cilium@v1.19.4`
🐹Go	`github.com/cilium/cilium`	≥ 1.18.2&&< 1.18.10	1.18.10`go get github.com/cilium/cilium@v1.18.10`
🐹Go	`github.com/cilium/cilium`	all versions	1.17.16`go get github.com/cilium/cilium@v1.17.16`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cilium/cilium, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cilium/cilium to 1.19.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53935 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### 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 p