CVE-2026-23274

netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels

Published Mar 20, 2026 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels

IDLETIMER revision 0 rules reuse existing timers by label and always call
mod_timer() on timer->timer.

If the label was created first by revision 1 with XT_IDLETIMER_ALARM,
the object uses alarm timer semantics and timer->timer is never initialized.
Reusing that object from revision 0 causes mod_timer() on an uninitialized
timer_list, triggering debugobjects warnings and possible panic when
panic_on_warn=1.

Fix this by rejecting revision 0 rule insertion when an existing timer with
the same label is of ALARM type.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4561-1 linux-6.1 security update
Debian DLA Debian DLA DLA-4606-1 linux security update
Debian DSA Debian DSA DSA-6238-1 linux security update
Debian DSA Debian DSA DSA-6243-1 linux security update
Ubuntu USN Ubuntu USN USN-8277-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8278-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8279-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8289-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8291-1 Linux kernel (Intel IoTG Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-8277-2 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-8291-2 Linux kernel (Low Latency) vulnerabilities
Ubuntu USN Ubuntu USN USN-8296-1 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8279-2 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8291-3 Linux kernel (Low Latency) vulnerabilities
Ubuntu USN Ubuntu USN USN-8296-2 Linux kernel (NVIDIA Tegra) vulnerabilities
Ubuntu USN Ubuntu USN USN-8279-3 Linux kernel (NVIDIA Tegra IGX) vulnerabilities
Ubuntu USN Ubuntu USN USN-8278-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8310-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8374-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8426-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8426-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8440-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8499-1 Linux kernel (Xilinx) vulnerabilities
Ubuntu USN Ubuntu USN USN-8508-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8528-1 Linux kernel (Xilinx ZynqMP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8289-2 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8393-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8439-1 Linux kernel (Oracle) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-758
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-908
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Weaknesses CWE-665
Type Values Removed Values Added
Weaknesses CWE-665
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels IDLETIMER revision 0 rules reuse existing timers by label and always call mod_timer() on timer->timer. If the label was created first by revision 1 with XT_IDLETIMER_ALARM, the object uses alarm timer semantics and timer->timer is never initialized. Reusing that object from revision 0 causes mod_timer() on an uninitialized timer_list, triggering debugobjects warnings and possible panic when panic_on_warn=1. Fix this by rejecting revision 0 rule insertion when an existing timer with the same label is of ALARM type.
Title netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Nov 10, 2026, 12:42 PM
Reserved
Jan 13, 2026, 3:37 PM
Status
Modified
Published
Mar 20, 2026, 9:16 AM
Modified
Nov 10, 2026, 1:18 PM
Severity
Moderate
Public date
Mar 20, 2026, 12:00 AM