CVE-2026-72247Network attack vector

Connection-limit bypass via misdirected zone comparison

Published Aug 15, 2026 · Updated Aug 15, 2026

Incorrect connection accounting in Linux netfilter nf_conncount allows remote attackers to bypass configured per-zone connection limits. Within __nf_conncount_add(), tuple-dedup checks pass a zone-direction bitmask where an original/reply enum is required, causing helpers to use the default zone ID and treat distinct zones as equal. Reachability requires nf_conncount-based limits with affected conntrack-zone directions; the resulting undercount defeats an availability control.

CVSS severity7.5
High
EPSS probability0.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Incorrect connection accounting in Linux netfilter nf_conncount allows remote attackers to bypass configured per-zone connection limits. Within __nf_conncount_add(), tuple-dedup checks pass a zone-direction bitmask where an original/reply enum is required, causing helpers to use the default zone ID and treat distinct zones as equal. Reachability requires nf_conncount-based limits with affected conntrack-zone directions; the resulting undercount defeats an availability control.

The record

CVE
CVE-2026-72247
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 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=21ba8847f857028dc83a0f341e16ecc616e34740 <35a56e2a46b90e6bd4ca816b80e9cb8d20dfc3ce
  2. Affected versionversion=21ba8847f857028dc83a0f341e16ecc616e34740 <3cd9a5792cbea81139c24320986dd0db69e9b5d0
  3. Affected versionversion=21ba8847f857028dc83a0f341e16ecc616e34740 <4f30a89c0ed2418719a1144881c2635b940b543d
  4. Affected versionversion=21ba8847f857028dc83a0f341e16ecc616e34740 <6ff07ac5405bea4d4ead3559fc123f987576424a
  5. Affected versionversion=21ba8847f857028dc83a0f341e16ecc616e34740 <78b5d6dbc860776161f9e9206b06ff8a01f531ab
  6. Affected versionversion=21ba8847f857028dc83a0f341e16ecc616e34740 <7bdc3c0985ecf17b957811fedcc684acdf698acc
  7. Affected versionversion=21ba8847f857028dc83a0f341e16ecc616e34740 <82fc35e0da9a91db9a034f8311f18f77a599ae3f
  8. Affected versionversion=21ba8847f857028dc83a0f341e16ecc616e34740 <f62c41b4910e65da396ec9a8c40c1fe7fe82e449
  9. Affected versionversion=4.14.92 <4.15
  10. Affected versionversion=4.18
  11. Affected versionversion=525e1dffed8711973f77412729621098a95238e5
  12. Affected versionversion=75af3d78168e654a5cd8bbc4c774f97be836165f

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=21ba8847f857028dc83a0f341e16ecc616e34740 <35a56e2a46b90e6bd4ca816b80e9cb8d20dfc3ce; version=21ba8847f857028dc83a0f341e16ecc616e34740 <3cd9a5792cbea81139c24320986dd0db69e9b5d0; version=21ba8847f857028dc83a0f341e16ecc616e34740 <4f30a89c0ed2418719a1144881c2635b940b543d; version=21ba8847f857028dc83a0f341e16ecc616e34740 <6ff07ac5405bea4d4ead3559fc123f987576424a; version=21ba8847f857028dc83a0f341e16ecc616e34740 <78b5d6dbc860776161f9e9206b06ff8a01f531ab; version=21ba8847f857028dc83a0f341e16ecc616e34740 <7bdc3c0985ecf17b957811fedcc684acdf698acc; version=21ba8847f857028dc83a0f341e16ecc616e34740 <82fc35e0da9a91db9a034f8311f18f77a599ae3f; version=21ba8847f857028dc83a0f341e16ecc616e34740 <f62c41b4910e65da396ec9a8c40c1fe7fe82e449; version=4.14.92 <4.15; version=4.18; version=525e1dffed8711973f77412729621098a95238e5; version=75af3d78168e654a5cd8bbc4c774f97be836165f

Published CVSS scores

7.5UbuntuCVSS:3.1/AV:N/AC:L/PR:N/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

T1499Endpoint Denial of Service

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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