Is CVE-2026-23405 in the CISA KEV catalog?

No. CVE-2026-23405 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-23405?

CVE-2026-23405 has a CVSS v3 base score of 6.5 (Moderate).

What is the EPSS score for CVE-2026-23405?

CVE-2026-23405 has an EPSS score of 0.18% (8th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-23405?

Upgrade linux on debian 11 to 5.10.251-1 or later. Fixes are available for 95 affected products.

CVE & CISA-KEV Catalog

CVE-2026-23405

MEDIUM

6.5

CVSS v3

NVD

Description

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix: limit the number of levels of policy namespaces Currently the number of policy namespaces is not bounded relying on the user namespace limit. However policy namespaces aren't strictly tied to user namespaces and it is possible to create them and nest them arbitrarily deep which can be used to exhaust system resource. Hard cap policy namespaces to the same depth as user namespaces.

How to fix

Remediation Available

linuxDebian

Fixed in:5.10.251-1CVE-2026-23405

Fixed in:6.1.164-1CVE-2026-23405

Fixed in:6.12.74-2CVE-2026-23405

Fixed in:6.19.6-2CVE-2026-23405

linuxUbuntu

Fixed in:4.15.0-249.261USN-8266-1

linux-awsUbuntu

Fixed in:4.15.0-1191.204USN-8266-1

linux-aws-fipsUbuntu

Fixed in:4.15.0-2129.135USN-8266-1

linux-aws-hweUbuntu

Fixed in:4.15.0-1191.204~16.04.1USN-8266-1

linux-azureUbuntu

Fixed in:4.15.0-1200.215~16.04.1USN-8267-1

Fixed in:5.15.0-1109.118USN-8163-2

linux-azure-4.15Ubuntu

Fixed in:4.15.0-1200.215USN-8266-1

linux-azure-5.15Ubuntu

Fixed in:5.15.0-1110.119~20.04.1USN-8243-1

linux-azure-5.4Ubuntu

Fixed in:5.4.0-1161.167~18.04.1USN-8201-1

linux-azure-fipsUbuntu

Fixed in:4.15.0-2109.115USN-8267-1

Fixed in:5.15.0-1109.118+fips1USN-8163-1

Fixed in:6.8.0-1052.58+fips1USN-8165-1

linux-bluefieldUbuntu

Fixed in:5.4.0-1116.123USN-8224-1

linux-fipsUbuntu

Fixed in:4.15.0-1146.158USN-8266-1

linux-gcpUbuntu

Fixed in:4.15.0-1184.201~16.04.1USN-8266-1

linux-gcp-4.15Ubuntu

Fixed in:4.15.0-1184.201USN-8266-1

linux-gcp-fipsUbuntu

Fixed in:4.15.0-2092.98USN-8266-1

linux-hweUbuntu

Fixed in:4.15.0-249.261~16.04.1USN-8266-1

linux-image-4.15.0-1146-fipsUbuntu

Fixed in:4.15.0-1146.158USN-8266-1

linux-image-4.15.0-1153-oracleUbuntu

Fixed in:4.15.0-1153.164~16.04.1USN-8267-1

Fixed in:4.15.0-1153.164USN-8266-1

linux-image-4.15.0-1173-kvmUbuntu

Fixed in:4.15.0-1173.178USN-8266-1

linux-image-4.15.0-1184-gcpUbuntu

Fixed in:4.15.0-1184.201~16.04.1USN-8266-1

Fixed in:4.15.0-1184.201USN-8266-1

linux-image-4.15.0-1191-awsUbuntu

Fixed in:4.15.0-1191.204~16.04.1USN-8266-1

Fixed in:4.15.0-1191.204USN-8266-1

linux-image-4.15.0-1200-azureUbuntu

Fixed in:4.15.0-1200.215~16.04.1USN-8267-1

Fixed in:4.15.0-1200.215USN-8266-1

linux-image-4.15.0-2092-gcp-fipsUbuntu

Fixed in:4.15.0-2092.98USN-8266-1

linux-image-4.15.0-2109-azure-fipsUbuntu

Fixed in:4.15.0-2109.115USN-8267-1

linux-image-4.15.0-2129-aws-fipsUbuntu

Fixed in:4.15.0-2129.135USN-8266-1

linux-image-4.15.0-249-genericUbuntu

Fixed in:4.15.0-249.261~16.04.1USN-8266-1

Fixed in:4.15.0-249.261USN-8266-1

linux-image-4.15.0-249-lowlatencyUbuntu

Fixed in:4.15.0-249.261~16.04.1USN-8266-1

Fixed in:4.15.0-249.261USN-8266-1

linux-image-5.15.0-1096-intel-iot-realtimeUbuntu

Fixed in:5.15.0-1096.98USN-8164-1

linux-image-5.15.0-1109-azureUbuntu

Fixed in:5.15.0-1109.118USN-8163-2

linux-image-5.15.0-1109-azure-fipsUbuntu

Fixed in:5.15.0-1109.118+fips1USN-8163-1

linux-image-5.15.0-1110-azureUbuntu

Fixed in:5.15.0-1110.119~20.04.1USN-8243-1

linux-image-5.4.0-1116-bluefieldUbuntu

Fixed in:5.4.0-1116.123USN-8224-1

linux-image-5.4.0-1139-raspiUbuntu

Fixed in:5.4.0-1139.152~18.04.1USN-8098-10

Fixed in:5.4.0-1139.152USN-8098-10

linux-image-5.4.0-1161-azureUbuntu

Fixed in:5.4.0-1161.167~18.04.1USN-8201-1

linux-image-6.17.0-1017-oemUbuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-image-6.8.0-1029-xilinxUbuntu

Fixed in:6.8.0-1029.30USN-8261-1

linux-image-6.8.0-1052-azure-fipsUbuntu

Fixed in:6.8.0-1052.58+fips1USN-8165-1

linux-image-aws-4.15Ubuntu

Fixed in:4.15.0.1191.189USN-8266-1

linux-image-aws-fipsUbuntu

Fixed in:4.15.0.2129.123USN-8266-1

linux-image-aws-fips-4.15Ubuntu

Fixed in:4.15.0.2129.123USN-8266-1

linux-image-aws-hweUbuntu

Fixed in:4.15.0.1191.204~16.04.1USN-8266-1

linux-image-aws-lts-18.04Ubuntu

Fixed in:4.15.0.1191.189USN-8266-1

linux-image-azureUbuntu

Fixed in:4.15.0.1200.215~16.04.1USN-8267-1

Fixed in:5.4.0.1161.167~18.04.1USN-8201-1

Fixed in:5.15.0.1110.119~20.04.1USN-8243-1

linux-image-azure-4.15Ubuntu

Fixed in:4.15.0.1200.168USN-8266-1

linux-image-azure-5.15Ubuntu

Fixed in:5.15.0.1110.119~20.04.1USN-8243-1

Fixed in:5.15.0.1109.107USN-8163-2

linux-image-azure-5.4Ubuntu

Fixed in:5.4.0.1161.167~18.04.1USN-8201-1

linux-image-azure-cvmUbuntu

Fixed in:5.15.0.1110.119~20.04.1USN-8243-1

linux-image-azure-fipsUbuntu

Fixed in:4.15.0.2109.105USN-8267-1

Fixed in:5.15.0.1109.94USN-8163-1

Fixed in:6.8.0-1052.58+fips1USN-8165-1

linux-image-azure-fips-4.15Ubuntu

Fixed in:4.15.0.2109.105USN-8267-1

linux-image-azure-fips-5.15Ubuntu

Fixed in:5.15.0.1109.94USN-8163-1

linux-image-azure-fips-6.8Ubuntu

Fixed in:6.8.0-1052.58+fips1USN-8165-1

linux-image-azure-lts-18.04Ubuntu

Fixed in:4.15.0.1200.168USN-8266-1

linux-image-azure-lts-22.04Ubuntu

Fixed in:5.15.0.1109.107USN-8163-2

linux-image-bluefieldUbuntu

Fixed in:5.4.0.1116.112USN-8224-1

linux-image-bluefield-5.4Ubuntu

Fixed in:5.4.0.1116.112USN-8224-1

linux-image-fipsUbuntu

Fixed in:4.15.0.1146.143USN-8266-1

linux-image-gcpUbuntu

Fixed in:4.15.0.1184.201~16.04.1USN-8266-1

linux-image-gcp-4.15Ubuntu

Fixed in:4.15.0.1184.197USN-8266-1

linux-image-gcp-fipsUbuntu

Fixed in:4.15.0.2092.90USN-8266-1

linux-image-gcp-fips-4.15Ubuntu

Fixed in:4.15.0.2092.90USN-8266-1

linux-image-gcp-lts-18.04Ubuntu

Fixed in:4.15.0.1184.197USN-8266-1

linux-image-genericUbuntu

Fixed in:4.15.0.249.233USN-8266-1

linux-image-generic-hwe-16.04Ubuntu

Fixed in:4.15.0.249.261~16.04.1USN-8266-1

linux-image-gkeUbuntu

Fixed in:4.15.0.1184.201~16.04.1USN-8266-1

linux-image-intel-iot-realtimeUbuntu

Fixed in:5.15.0.1096.100USN-8164-1

linux-image-intel-iot-realtime-5.15Ubuntu

Fixed in:5.15.0.1096.100USN-8164-1

linux-image-kvmUbuntu

Fixed in:4.15.0.1173.164USN-8266-1

linux-image-lowlatencyUbuntu

Fixed in:4.15.0.249.233USN-8266-1

linux-image-lowlatency-hwe-16.04Ubuntu

Fixed in:4.15.0.249.261~16.04.1USN-8266-1

linux-image-oemUbuntu

Fixed in:4.15.0.249.261~16.04.1USN-8266-1

linux-image-oem-24.04Ubuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-image-oem-24.04aUbuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-image-oem-24.04bUbuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-image-oem-24.04cUbuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-image-oem-24.04dUbuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-image-oem-6.17Ubuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-image-oracleUbuntu

Fixed in:4.15.0.1153.164~16.04.1USN-8267-1

linux-image-oracle-4.15Ubuntu

Fixed in:4.15.0.1153.158USN-8266-1

linux-image-oracle-lts-18.04Ubuntu

Fixed in:4.15.0.1153.158USN-8266-1

linux-image-raspiUbuntu

Fixed in:5.4.0.1139.170USN-8098-10

linux-image-raspi-5.4Ubuntu

Fixed in:5.4.0.1139.152~18.04.1USN-8098-10

Fixed in:5.4.0.1139.170USN-8098-10

linux-image-raspi-hwe-18.04Ubuntu

Fixed in:5.4.0.1139.152~18.04.1USN-8098-10

linux-image-raspi2Ubuntu

Fixed in:5.4.0.1139.170USN-8098-10

linux-image-virtualUbuntu

Fixed in:4.15.0.249.233USN-8266-1

linux-image-virtual-hwe-16.04Ubuntu

Fixed in:4.15.0.249.261~16.04.1USN-8266-1

linux-image-xilinxUbuntu

Fixed in:6.8.0.1029.30USN-8261-1

linux-image-xilinx-6.8Ubuntu

Fixed in:6.8.0.1029.30USN-8261-1

linux-image-xilinx-zynqmpUbuntu

Fixed in:6.8.0.1029.30USN-8261-1

linux-intel-iot-realtimeUbuntu

Fixed in:5.15.0-1096.98USN-8164-1

linux-kvmUbuntu

Fixed in:4.15.0-1173.178USN-8266-1

linux-oem-6.17Ubuntu

Fixed in:6.17.0-1017.17USN-8152-1

linux-oracleUbuntu

Fixed in:4.15.0-1153.164~16.04.1USN-8267-1

Fixed in:4.15.0-1153.164USN-8266-1

linux-raspiUbuntu

Fixed in:5.4.0-1139.152USN-8098-10

linux-raspi-5.4Ubuntu

Fixed in:5.4.0-1139.152~18.04.1USN-8098-10

linux-xilinxUbuntu

Fixed in:6.8.0-1029.30USN-8261-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Exploit Intelligence

0.18%probability of exploitation in 30 days

8thpercentile

Low risk: more likely to be exploited than 8% of all known CVEs.

References

Patch8

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-24.