CVE-2026-33726

Ingress policy bypass via skipped datapath hairpin

Published Mar 27, 2026 · Updated Mar 27, 2026

Authorization bypass in Cilium before 1.17.14, 1.18.0 through 1.18.7, and 1.19.0 through 1.19.1 allows remote authenticated users to bypass policy. After Envoy forwards L7 service traffic to a same-node backend, the cil_to_container path accepts the packet without hairpinning it through ingress policy enforcement. Reachability requires per-endpoint routing with BPF host routing disabled; traffic denied by ingress policy can consequently reach the local backend.

CVSS severity5.4
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in Cilium before 1.17.14, 1.18.0 through 1.18.7, and 1.19.0 through 1.19.1 allows remote authenticated users to bypass policy. After Envoy forwards L7 service traffic to a same-node backend, the cil_to_container path accepts the packet without hairpinning it through ingress policy enforcement. Reachability requires per-endpoint routing with BPF host routing disabled; traffic denied by ingress policy can consequently reach the local backend.

The record

CVE
CVE-2026-33726
Published
Mar 27, 2026
Updated
Mar 27, 2026
Vendor
Cilium
Product
Cilium
Classifications
CWE-863, CWE-284, T1210
Attack vector
adjacent
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.17.14
  2. Affected versionversion=>= 1.18.0, < 1.18.8
  3. Affected versionversion=>= 1.19.0, < 1.19.2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesauthenticated

What is affected?

Cilium · Ciliumversion=< 1.17.14; version=>= 1.18.0, < 1.18.8; version=>= 1.19.0, < 1.19.2

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.4GitHub, Inc.CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
CWE-284Improper Access Control
T1210Exploitation of Remote Services

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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