CVE-2026-52920Network attack vector

Policy bypass via reversed strict-rule indexing

Published Jun 24, 2026 · Updated Jun 24, 2026

Incorrect inbound IPsec policy matching in the Linux Kernel allows remote authenticated users to bypass multi-element strict rules. match_policy_in() traverses security-path transforms in reverse but previously indexed the forward rule array with a negative-derived position, pairing transforms with the wrong policy elements. Exposure requires an inbound IPsec packet with multiple transforms and an xt_policy rule using --strict; the error can accept or reject traffic against the wrong element.

CVSS severity8.3
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect inbound IPsec policy matching in the Linux Kernel allows remote authenticated users to bypass multi-element strict rules. match_policy_in() traverses security-path transforms in reverse but previously indexed the forward rule array with a negative-derived position, pairing transforms with the wrong policy elements. Exposure requires an inbound IPsec packet with multiple transforms and an xt_policy rule using --strict; the error can accept or reject traffic against the wrong element.

The record

CVE
CVE-2026-52920
Published
Jun 24, 2026
Updated
Jun 24, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
Unavailable
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 24, 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=2.6.17
  2. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <392cc1d8408b5665215c1e9290bbf0f92339b043
  3. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <4b2b4d7d4e203c92db8966b163edfacb1f0e1e29
  4. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <82664d0f1ba25e4f9a71994954abae24c60f4067
  5. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <938867e870fb5471bb16f442aeac81326e05bf65
  6. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <b130a6eefa02bd4d475f2f059da8bcfb3e7d18d9
  7. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <eb323f7b82d2e2f638de0cc2a177803eb20e0707
  8. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <f98b7f85e04b40e28b08c461ded0cc79f14f5509
  9. Affected versionversion=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <fc1c518bb1f054831ecabb32da9b8e1dff9699c6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.17; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <392cc1d8408b5665215c1e9290bbf0f92339b043; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <4b2b4d7d4e203c92db8966b163edfacb1f0e1e29; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <82664d0f1ba25e4f9a71994954abae24c60f4067; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <938867e870fb5471bb16f442aeac81326e05bf65; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <b130a6eefa02bd4d475f2f059da8bcfb3e7d18d9; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <eb323f7b82d2e2f638de0cc2a177803eb20e0707; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <f98b7f85e04b40e28b08c461ded0cc79f14f5509; version=c4b885139203d37f76662c37ae645fe8e0f4e4e5 <fc1c518bb1f054831ecabb32da9b8e1dff9699c6

Published CVSS scores

8.3Linux kernel CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/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
Privilegesauthenticated
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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