CVE-2025-21823: batman-adv: Drop unmanaged ELP metric worker

Q: What is the severity of CVE-2025-21823?

CVE-2025-21823 is classified as a medium severity vulnerability in the Linux kernel.

Q: How do I fix CVE-2025-21823?

To fix CVE-2025-21823, ensure you update your Linux kernel and batman-adv to the latest patched version.

Q: What systems are affected by CVE-2025-21823?

CVE-2025-21823 affects the Linux kernel and the batman-adv networking layer upstream.

Q: What does CVE-2025-21823 impact?

CVE-2025-21823 could potentially affect network stability and performance due to improper locking mechanisms.

Q: Is CVE-2025-21823 exploited in the wild?

As of now, there is no evidence that CVE-2025-21823 is being actively exploited in the wild.

Published Feb 27, 2025

Updated

In the Linux kernel, the following vulnerability has been resolved:

batman-adv: Drop unmanaged ELP metric worker

The ELP worker needs to calculate new metric values for all neighbors "reachable" over an interface. Some of the used metric sources require locks which might need to sleep. This sleep is incompatible with the RCU list iterator used for the recorded neighbors. The initial approach to work around of this problem was to queue another work item per neighbor and then run this in a new context.

Even when this solved the RCU vs mightsleep() conflict, it has a major problems: Nothing was stopping the work item in case it is not needed anymore - for example because one of the related interfaces was removed or the batman-adv module was unloaded - resulting in potential invalid memory accesses.

Directly canceling the metric worker also has various problems:

cancelworksync for a to-be-deactivated interface is called with rtnllock held. But the code in the ELP metric worker also tries to use rtnllock() - which will never return in this case. This also means that cancelworksync would never return because it is waiting for the worker to finish. iterating over the neighbor list for the to-be-deactivated interface is currently done using the RCU specific methods. Which means that it is possible to miss items when iterating over it without the associated spinlock - a behaviour which is acceptable for a periodic metric check but not for a cleanup routine (which must "stop" all still running workers)

The better approch is to get rid of the per interface neighbor metric worker and handle everything in the interface worker. The original problems are solved by:

creating a list of neighbors which require new metric information inside the RCU protected context, gathering the metric according to the new list outside the RCU protected context only use rcutrylock inside metric gathering code to avoid a deadlock when the canceldelayedworksync is called in the interface removal code (which is called with the rtnllock held)

Affected Software

212 affected componentsFixes available

Linux Kernel

Linux batman-adv

Linux Linux kernel>=4.6<5.4.291

Linux Linux kernel>=5.5<5.10.235

Linux Linux kernel>=5.11<5.15.179

Linux Linux kernel>=5.16<6.1.129

Linux Linux kernel>=6.2<6.6.79

Linux Linux kernel>=6.7<6.12.16

Linux Linux kernel>=6.13<6.13.4

Linux Linux kernel=6.14-rc1

Linux Linux kernel=6.14-rc2

ubuntu/linux-azure*

ubuntu/linux-aws-hwe*

ubuntu/linux-azure*

ubuntu/linux-gcp*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oracle*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4<5.4.0-1146.156~18.04.1

5.4.0-1146.156~18.04.1

ubuntu/linux-azure*

ubuntu/linux-azure-4.15*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4<5.4.0-1151.158~18.04.1

5.4.0-1151.158~18.04.1

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-4.15*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4<5.4.0-1149.158~18.04.1

5.4.0-1149.158~18.04.1

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4<5.4.0-216.236~18.04.1

5.4.0-216.236~18.04.1

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4<5.4.0-1092.97~18.04.1

5.4.0-1092.97~18.04.1

ubuntu/linux-kvm*

ubuntu/linux-oem*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4<5.4.0-1144.154~18.04.1

5.4.0-1144.154~18.04.1

ubuntu/linux-raspi-5.4<5.4.0-1129.142~18.04.1

5.4.0-1129.142~18.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.4.0-216.236

5.4.0-216.236

ubuntu/linux-aws<5.4.0-1146.156

5.4.0-1146.156

ubuntu/linux-aws-5.15<5.15.0-1084.91~20.04.1

5.15.0-1084.91~20.04.1

ubuntu/linux-azure<5.4.0-1151.158

5.4.0-1151.158

ubuntu/linux-azure-5.15<5.15.0-1089.98~20.04.1

5.15.0-1089.98~20.04.1

ubuntu/linux-bluefield<5.4.0-1105.112

5.4.0-1105.112

ubuntu/linux-gcp<5.4.0-1149.158

5.4.0-1149.158

ubuntu/linux-gcp-5.15<5.15.0-1083.92~20.04.1

5.15.0-1083.92~20.04.1

ubuntu/linux-ibm<5.4.0-1092.97

5.4.0-1092.97

ubuntu/linux-ibm-5.15<5.15.0-1076.79~20.04.1

5.15.0-1076.79~20.04.1

ubuntu/linux-intel-iotg-5.15<5.15.0-1079.85~20.04.1

5.15.0-1079.85~20.04.1

ubuntu/linux-kvm<5.4.0-1133.142

5.4.0-1133.142

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-140.150~20.04.1

5.15.0-140.150~20.04.1

ubuntu/linux-oracle<5.4.0-1144.154

5.4.0-1144.154

ubuntu/linux-oracle-5.15<5.15.0-1081.87~20.04.1

5.15.0-1081.87~20.04.1

ubuntu/linux-raspi<5.4.0-1129.142

5.4.0-1129.142

ubuntu/linux-riscv-5.15<5.15.0-1079.83~20.04.1

5.15.0-1079.83~20.04.1

ubuntu/linux-xilinx-zynqmp<5.4.0-1064.68

5.4.0-1064.68

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

ubuntu/linux-gke-5.15*

ubuntu/linux-gkeop*

ubuntu/linux-gkeop-5.15*

ubuntu/linux-hwe-5.11*

ubuntu/linux-hwe-5.13*

ubuntu/linux-hwe-5.15<5.15.0-142.152~20.04.1

5.15.0-142.152~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-intel-5.13*

ubuntu/linux-iot<5.4.0-1051.54

5.4.0-1051.54

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1039.39~20.04.1

5.15.0-1039.39~20.04.1

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.8*

ubuntu/linux-aws-fips<5.4.0-1146.156+fips1

5.4.0-1146.156+fips1

ubuntu/linux-azure-fips<5.4.0-1151.158+fips1

5.4.0-1151.158+fips1

ubuntu/linux-fips<5.4.0-1120.130

5.4.0-1120.130

ubuntu/linux-gcp-fips<5.4.0-1149.158+fips1

5.4.0-1149.158+fips1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.15.0-140.150

5.15.0-140.150

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1084.91

5.15.0-1084.91

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1035.37~22.04.1

6.8.0-1035.37~22.04.1

ubuntu/linux-azure<5.15.0-1089.98

5.15.0-1089.98

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1034.39~22.04.1

6.8.0-1034.39~22.04.1

ubuntu/linux-azure-fde<5.15.0-1089.98.1

5.15.0-1089.98.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-gcp<5.15.0-1083.92

5.15.0-1083.92

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1036.38~22.04.1

6.8.0-1036.38~22.04.1

ubuntu/linux-gke<5.15.0-1081.87

5.15.0-1081.87

ubuntu/linux-gkeop<5.15.0-1066.74

5.15.0-1066.74

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-78.78~22.04.1

6.8.0-78.78~22.04.1

ubuntu/linux-ibm<5.15.0-1076.79

5.15.0-1076.79

ubuntu/linux-ibm-6.8<6.8.0-1033.33~22.04.1

6.8.0-1033.33~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1079.85

5.15.0-1079.85

ubuntu/linux-kvm<5.15.0-1080.85

5.15.0-1080.85

ubuntu/linux-lowlatency<5.15.0-140.150

5.15.0-140.150

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-78.78.1~22.04.1

6.8.0-78.78.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1078.79

5.15.0-1078.79

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1035.38~22.04.1

6.8.0-1035.38~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1037.37

5.15.0-1037.37

ubuntu/linux-nvidia-tegra-igx<5.15.0-1026.26

5.15.0-1026.26

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1081.87

5.15.0-1081.87

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1032.33~22.04.1

6.8.0-1032.33~22.04.1

ubuntu/linux-raspi<5.15.0-1078.81

5.15.0-1078.81

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-78.78~22.04.1

6.8.0-78.78~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1050.54

5.15.0-1050.54

ubuntu/linux-bluefield<5.15.0-1066.68

5.15.0-1066.68

ubuntu/linux-intel-iot-realtime<5.15.0-1077.79

5.15.0-1077.79

ubuntu/linux-realtime<5.15.0-1084.93

5.15.0-1084.93

ubuntu/linux-realtime-6.8<6.8.1-1030.31~22.04.1

6.8.1-1030.31~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1084.91+fips1

5.15.0-1084.91+fips1

ubuntu/linux-azure-fips<5.15.0-1089.98+fips1

5.15.0-1089.98+fips1

ubuntu/linux-fips<5.15.0-140.150+fips1

5.15.0-140.150+fips1

ubuntu/linux-gcp-fips<5.15.0-1083.92+fips1

5.15.0-1083.92+fips1

ubuntu/linux<6.8.0-78.78

6.8.0-78.78

ubuntu/linux-aws<6.8.0-1035.37

6.8.0-1035.37

ubuntu/linux-azure<6.8.0-1034.39

6.8.0-1034.39

ubuntu/linux-azure-6.11<6.11.0-1015.15~24.04.1

6.11.0-1015.15~24.04.1

ubuntu/linux-azure-nvidia<6.8.0-1022.23

6.8.0-1022.23

ubuntu/linux-gcp<6.8.0-1036.38

6.8.0-1036.38

ubuntu/linux-gcp-6.11<6.11.0-1015.15~24.04.1

6.11.0-1015.15~24.04.1

ubuntu/linux-gke<6.8.0-1032.36

6.8.0-1032.36

ubuntu/linux-gkeop<6.8.0-1019.21

6.8.0-1019.21

ubuntu/linux-hwe-6.11<6.11.0-26.26~24.04.1

6.11.0-26.26~24.04.1

ubuntu/linux-ibm<6.8.0-1033.33

6.8.0-1033.33

ubuntu/linux-intel*

ubuntu/linux-lowlatency<6.8.0-78.78.1

6.8.0-78.78.1

ubuntu/linux-lowlatency-hwe-6.11<6.11.0-1014.15~24.04.1

6.11.0-1014.15~24.04.1

ubuntu/linux-nvidia<6.8.0-1035.38

6.8.0-1035.38

ubuntu/linux-nvidia-6.11<6.11.0-1010.10

6.11.0-1010.10

ubuntu/linux-nvidia-lowlatency<6.8.0-1035.38.1

6.8.0-1035.38.1

ubuntu/linux-nvidia-tegra<6.8.0-1009.9

6.8.0-1009.9

ubuntu/linux-oem-6.11<6.11.0-1022.22

6.11.0-1022.22

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1032.33

6.8.0-1032.33

ubuntu/linux-raspi<6.8.0-1035.39

6.8.0-1035.39

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-xilinx<6.8.0-1017.18

6.8.0-1017.18

ubuntu/linux-raspi-realtime<6.8.0-2028.29

6.8.0-2028.29

ubuntu/linux-realtime<6.8.1-1030.31

6.8.1-1030.31

ubuntu/linux-fips<6.8.0-78.78+fips1

6.8.0-78.78+fips1

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

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Fixed in 5.4.0-1146.156~18.04.1
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Fixed in 5.4.0-1151.158~18.04.1
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Fixed in 5.4.0-1149.158~18.04.1
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Fixed in 5.4.0-216.236~18.04.1
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Fixed in 5.4.0-1092.97~18.04.1
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Fixed in 5.4.0-1144.154~18.04.1
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Fixed in 5.4.0-1129.142~18.04.1
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Fixed in 5.4.0-216.236
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Fixed in 5.4.0-1146.156
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Fixed in 5.15.0-1084.91~20.04.1
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Fixed in 5.4.0-1151.158
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Fixed in 5.15.0-1089.98~20.04.1
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Fixed in 5.4.0-1105.112
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Fixed in 5.4.0-1149.158
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Fixed in 5.15.0-1083.92~20.04.1
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Fixed in 5.4.0-1092.97
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Fixed in 5.15.0-1076.79~20.04.1
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Fixed in 5.15.0-1079.85~20.04.1
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Fixed in 5.4.0-1133.142
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Fixed in 5.15.0-140.150~20.04.1
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Fixed in 5.4.0-1144.154
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Fixed in 5.15.0-1081.87~20.04.1
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Fixed in 5.4.0-1129.142
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Fixed in 5.15.0-1079.83~20.04.1
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Fixed in 5.4.0-1064.68
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Fixed in 5.15.0-142.152~20.04.1
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Fixed in 5.4.0-1051.54
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Fixed in 5.15.0-1039.39~20.04.1
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Fixed in 5.4.0-1146.156+fips1
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Fixed in 5.4.0-1151.158+fips1
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Fixed in 5.4.0-1120.130
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Fixed in 5.4.0-1149.158+fips1
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Fixed in 5.15.0-140.150
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Fixed in 5.15.0-1084.91
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Fixed in 6.8.0-1035.37~22.04.1
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Fixed in 5.15.0-1089.98
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Fixed in 6.8.0-1034.39~22.04.1
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Fixed in 5.15.0-1089.98.1
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Fixed in 5.15.0-1083.92
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Fixed in 6.8.0-1036.38~22.04.1
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Fixed in 5.15.0-1081.87
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Fixed in 5.15.0-1066.74
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Fixed in 6.8.0-78.78~22.04.1
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Fixed in 5.15.0-1076.79
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Fixed in 6.8.0-1033.33~22.04.1
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Fixed in 5.15.0-1079.85
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Fixed in 5.15.0-1080.85
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Fixed in 5.15.0-140.150
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Fixed in 6.8.0-78.78.1~22.04.1
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Fixed in 5.15.0-1078.79
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Fixed in 6.8.0-1035.38~22.04.1
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Fixed in 5.15.0-1037.37
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Fixed in 5.15.0-1026.26
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Fixed in 5.15.0-1081.87
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Fixed in 6.8.0-1032.33~22.04.1
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Fixed in 5.15.0-1078.81
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Fixed in 6.8.0-78.78~22.04.1
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Fixed in 5.15.0-1050.54
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Fixed in 5.15.0-1066.68
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Fixed in 5.15.0-1077.79
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Fixed in 5.15.0-1084.93
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Fixed in 6.8.1-1030.31~22.04.1
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Fixed in 5.15.0-1084.91+fips1
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Fixed in 5.15.0-1089.98+fips1
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Fixed in 5.15.0-140.150+fips1
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Fixed in 5.15.0-1083.92+fips1
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Fixed in 6.8.0-78.78
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Fixed in 6.8.0-1035.37
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Fixed in 6.8.0-1034.39
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Fixed in 6.11.0-1015.15~24.04.1
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Fixed in 6.8.0-1022.23
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Fixed in 6.8.0-1036.38
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Fixed in 6.11.0-1015.15~24.04.1
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Fixed in 6.8.0-1032.36
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Fixed in 6.8.0-1019.21
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Fixed in 6.11.0-26.26~24.04.1
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Fixed in 6.8.0-1033.33
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Fixed in 6.8.0-78.78.1
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Fixed in 6.11.0-1014.15~24.04.1
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Fixed in 6.8.0-1035.38
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Fixed in 6.11.0-1010.10
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Fixed in 6.8.0-1035.38.1
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Fixed in 6.8.0-1009.9
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Fixed in 6.11.0-1022.22
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Fixed in 6.8.0-1032.33
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Fixed in 6.8.0-1035.39
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Fixed in 6.8.0-1017.18
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Fixed in 6.8.0-2028.29
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Fixed in 6.8.1-1030.31
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Fixed in 6.8.0-78.78+fips1

Event History

Feb 27, 2025

CVE Published

via MITRE·08:06 PM

Data Sourced

via MITRE·08:06 PM

DescriptionSeverity

Data Sourced

via OSV·08:16 PM

DescriptionSeverityAffected Software

Event

via OSV·08:16 PM

Data Sourced

via NVD·08:16 PM

RemedyDescriptionSeverityAffected Software

Frequently Asked Questions

What is the severity of CVE-2025-21823?

CVE-2025-21823 is classified as a medium severity vulnerability in the Linux kernel.

How do I fix CVE-2025-21823?

To fix CVE-2025-21823, ensure you update your Linux kernel and batman-adv to the latest patched version.

What systems are affected by CVE-2025-21823?

CVE-2025-21823 affects the Linux kernel and the batman-adv networking layer upstream.

What does CVE-2025-21823 impact?

CVE-2025-21823 could potentially affect network stability and performance due to improper locking mechanisms.

Is CVE-2025-21823 exploited in the wild?

As of now, there is no evidence that CVE-2025-21823 is being actively exploited in the wild.

CVE-2025-21823: batman-adv: Drop unmanaged ELP metric worker

Affected Software

Remediation

Event History

Frequently Asked Questions

What is the severity of CVE-2025-21823?

How do I fix CVE-2025-21823?

What systems are affected by CVE-2025-21823?

What does CVE-2025-21823 impact?

Is CVE-2025-21823 exploited in the wild?

Company

Resources

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