CVE-2025-22021Network attack vector

Network policy bypass via missing IPv6 conntrack lookup

Published Apr 16, 2025 · Updated Aug 5, 2026

Improper packet handling in affected Linux kernels allows remote attackers to bypass IPv6 socket-based policy enforcement via SNAT traffic. The nf_sk_lookup_slow_v6 path fails to recover the original conntrack five-tuple for SNATed IPv6 packets, so xt_socket cannot identify the transparent socket. Exposure requires IPv6 SNAT plus transparent-socket policy routing, such as the Cilium and Envoy path described by kernel.org, and permits traffic to evade the intended Layer 7 redirect.

CVSS severity10.0
Critical
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper packet handling in affected Linux kernels allows remote attackers to bypass IPv6 socket-based policy enforcement via SNAT traffic. The nf_sk_lookup_slow_v6 path fails to recover the original conntrack five-tuple for SNATed IPv6 packets, so xt_socket cannot identify the transparent socket. Exposure requires IPv6 SNAT plus transparent-socket policy routing, such as the Cilium and Envoy path described by kernel.org, and permits traffic to evade the intended Layer 7 redirect.

The record

CVE
CVE-2025-22021
Published
Apr 16, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1562.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=3.13
  2. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <1ca2169cc19dca893c7aae6af122852097435d16
  3. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <1ec43100f7123010730b7ddfc3d5c2eac19e70e7
  4. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <221c27259324ec1404f028d4f5a0f2ae7f63ee23
  5. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <2bb139e483f8cbe488d19d8c1135ac3615e2668c
  6. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <41904cbb343d115931d6bf79aa2c815cac4ef72b
  7. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <5251041573850e5020cd447374e23010be698898
  8. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <58ab63d3ded2ca6141357a2b24eee8453d0f871d
  9. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <6488b96a79a26e19100ad872622f04e93b638d7f
  10. Affected versionversion=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <932b32ffd7604fb00b5c57e239a3cc4d901ccf6e

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.13; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <1ca2169cc19dca893c7aae6af122852097435d16; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <1ec43100f7123010730b7ddfc3d5c2eac19e70e7; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <221c27259324ec1404f028d4f5a0f2ae7f63ee23; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <2bb139e483f8cbe488d19d8c1135ac3615e2668c; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <41904cbb343d115931d6bf79aa2c815cac4ef72b; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <5251041573850e5020cd447374e23010be698898; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <58ab63d3ded2ca6141357a2b24eee8453d0f871d; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <6488b96a79a26e19100ad872622f04e93b638d7f; version=eb31628e37a0a4e01fffd79dcc7f815d2357f53a <932b32ffd7604fb00b5c57e239a3cc4d901ccf6e

Published CVSS scores

10.0kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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.

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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

T1562.004Impair Defenses: Disable or Modify System Firewall

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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