CVE-2026-53269

Local service interruption via SYNPROXY refcount race

Published Jun 25, 2026 · Updated Jun 25, 2026

Race condition in Linux Kernel allows local users to interrupt service by concurrently creating the first SYNPROXY rules. The iptables target and nftables expression frontends update shared hook reference counts without serialization, allowing simultaneous first registrations to race. Local privileges sufficient to create SYNPROXY rules are required, and the documented consequence is availability loss rather than data access or modification.

CVSS severity5.5
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Linux Kernel allows local users to interrupt service by concurrently creating the first SYNPROXY rules. The iptables target and nftables expression frontends update shared hook reference counts without serialization, allowing simultaneous first registrations to race. Local privileges sufficient to create SYNPROXY rules are required, and the documented consequence is availability loss rather than data access or modification.

The record

CVE
CVE-2026-53269
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499
Attack vector
local
Privileges
authenticated

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=5.3
  2. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <0ec9ddc1bda261a2c57636c74c8b4e53000102c9
  3. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <0f8ba5e4c53d2e4a536aa68140beda9fe59b2f88
  4. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <2fcba19caaeb2a33017459d3430f057967bb91b6
  5. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <56ffbe3a08c01dcdb0d6adee9ce1e535bfb3b389
  6. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <640441348258220e78daed40528b85b8afcedab6
  7. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <aaf80701dc2f7a48fe543961e21f8ca3924d587c
  8. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <debc57b83d5b323df74bf010c8d50fe26ad2ed6b
  9. Affected versionversion=ad49d86e07a497e834cb06f2b151dccd75f8e148 <fbf0591275f50eae5733c3d7a8cd6c1e79933ffa

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.3; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <0ec9ddc1bda261a2c57636c74c8b4e53000102c9; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <0f8ba5e4c53d2e4a536aa68140beda9fe59b2f88; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <2fcba19caaeb2a33017459d3430f057967bb91b6; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <56ffbe3a08c01dcdb0d6adee9ce1e535bfb3b389; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <640441348258220e78daed40528b85b8afcedab6; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <aaf80701dc2f7a48fe543961e21f8ca3924d587c; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <debc57b83d5b323df74bf010c8d50fe26ad2ed6b; version=ad49d86e07a497e834cb06f2b151dccd75f8e148 <fbf0591275f50eae5733c3d7a8cd6c1e79933ffa

Published CVSS scores

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.

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)
Vectorlocal
Privilegesauthenticated
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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