CVE-2026-53221Network attack vector

Policy-boundary disclosure and injection via tunnel misselection

Published Jun 25, 2026 · Updated Jun 25, 2026

Incorrect IPv6 VTI tunnel matching in affected Linux Kernel releases allows remote attackers to cross tunnel policy boundaries via IPv6 traffic. The vti6_tnl_lookup() fallback loops search the shared tnls_r_l hash table without verifying that a colliding candidate has the required wildcard local or remote address. Exploitation requires a VTI6 configuration with colliding exact and wildcard entries; crafted packets can then enter the wrong interface, mark, and policy context, enabling cross-tunnel traffic disclosure, injection, or disruption.

CVSS severity9.8
Critical
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect IPv6 VTI tunnel matching in affected Linux Kernel releases allows remote attackers to cross tunnel policy boundaries via IPv6 traffic. The vti6_tnl_lookup() fallback loops search the shared tnls_r_l hash table without verifying that a colliding candidate has the required wildcard local or remote address. Exploitation requires a VTI6 configuration with colliding exact and wildcard entries; crafted packets can then enter the wrong interface, mark, and policy context, enabling cross-tunnel traffic disclosure, injection, or disruption.

The record

CVE
CVE-2026-53221
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 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=3.19
  2. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <2abfb19bbb81958714ad1d43ebeb65b30394184b
  3. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <2fc7bc087cc7085368263d9d37bfe9a0bddd6a2d
  4. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <47fb3c2b4203556308e64354b3e78f2ce221d646
  5. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <90fd4513315ca07da99cfd8549d3e553a7160f0d
  6. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <a5c0359f5cbc51a2e2b114d6041e0f3c73f903e9
  7. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <c327fa4fca31415431202e063767a7ae342e19c6
  8. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <f513f308cc4bdb4530d033431592ffbc29b7fca1
  9. Affected versionversion=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <fc657ac0767c49839b3ef0b08dc0953ca30883f8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=3.19; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <2abfb19bbb81958714ad1d43ebeb65b30394184b; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <2fc7bc087cc7085368263d9d37bfe9a0bddd6a2d; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <47fb3c2b4203556308e64354b3e78f2ce221d646; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <90fd4513315ca07da99cfd8549d3e553a7160f0d; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <a5c0359f5cbc51a2e2b114d6041e0f3c73f903e9; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <c327fa4fca31415431202e063767a7ae342e19c6; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <f513f308cc4bdb4530d033431592ffbc29b7fca1; version=fbe68ee87522f6eaa10f9076c0a7117e1613f2f7 <fc657ac0767c49839b3ef0b08dc0953ca30883f8

Published CVSS scores

9.8LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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