CVE-2023-42756Public exploit

Local system crash via mismatched ipset reference counting

Published Sep 28, 2023 · Updated Nov 6, 2025

Race condition in Netfilter ipset in Red Hat Enterprise Linux 9 allows local users to crash the system by racing set operations. During a retried call_ad operation, code increments set->ref instead of ref_netlink, mismatching cleanup and allowing a swapped set to reach BUG_ON. Triggering requires local access and privileges to issue ipset netlink commands; successful exploitation panics the kernel and interrupts the host.

CVSS severity4.4
Medium
EPSS probability0.27%
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 Netfilter ipset in Red Hat Enterprise Linux 9 allows local users to crash the system by racing set operations. During a retried call_ad operation, code increments set->ref instead of ref_netlink, mismatching cleanup and allowing a swapped set to reach BUG_ON. Triggering requires local access and privileges to issue ipset netlink commands; successful exploitation panics the kernel and interrupts the host.

The record

CVE
CVE-2023-42756
Published
Sep 28, 2023
Updated
Nov 6, 2025
Vendor
Red Hat
Product
Red Hat Enterprise Linux 9
Classifications
CWE-362, T1499
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Sep 28, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 6, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Red Hat · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.

Published CVSS scores

4.7NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
4.4Red Hat, Inc.CVSS:3.1/AV:L/AC:L/PR:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499Endpoint Denial of Service

Public exploit references

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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