UBUNTU-CVE-2025-37949: Null Pointer Dereference

Q: Which systems are exposed to this issue?

The affected software list includes Ubuntu kernels: linux, linux-aws-fips, linux-azure-fips, linux-fips, linux-gcp-fips, linux-azure, linux-gcp, and linux-oracle. The fault occurs in xenbus request handling, so exposure depends on use of the Xen bus subsystem.

Q: What access does an attacker need to exploit it?

The severity vector specifies local attack access, low attack complexity, low privileges required, and no user interaction. The reported impact is availability only; confidentiality and integrity impacts are listed as none.

Q: What failure should operators look for?

The reported symptom is a kernel NULL pointer dereference in the xenbus_thread call stack, involving __wake_up_common, process_msg, and xenbus_thread. This can occur when a Xenbus request is freed after waking a waiting caller while xenbus_thread still accesses the request.

Q: What change resolves the lifetime race?

The resolution tracks each Xenbus request with two krefs: one held by the caller and one held by xenbus_thread. Each holder releases its reference when finished, and the request is freed only after the final kref_put().

Published May 20, 2025

Updated

In the Linux kernel, the following vulnerability has been resolved: xenbus: Use kref to track req lifetime Marek reported seeing a NULL pointer fault in the xenbusthread callstack: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: e030:wakeupcommon+0x4c/0x180 Call Trace: <TASK> wakeupcommonlock+0x82/0xd0 processmsg+0x18e/0x2f0 xenbusthread+0x165/0x1c0 processmsg+0x18e is req->cb(req). req->cb is set to xswakeup(), a thin wrapper around wakeup(), or xenbusdevqueuereply(). It seems like it was xswakeup() in this case. It seems like req may have woken up the xswaitforreply(), which kfree()ed the req. When xenbusthread resumes, it faults on the zero-ed data. Linux Device Drivers 2nd edition states: "Normally, a wakeup call can cause an immediate reschedule to happen, meaning that other processes might run before wakeup returns." ... which would match the behaviour observed. Change to keeping two krefs on each request. One for the caller, and one for xenbusthread. Each will krefput() when finished, and the last will free it. This use of kref matches the description in Documentation/core-api/kref.rst

Affected Software

214 affected componentsFixes available

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*

ubuntu/linux-azure*

ubuntu/linux-azure-4.15*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-4.15*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4*

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4*

ubuntu/linux-kvm*

ubuntu/linux-oem*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4*

ubuntu/linux-raspi-5.4*

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*

ubuntu/linux-aws*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1088.95~20.04.1

5.15.0-1088.95~20.04.1

ubuntu/linux-aws-5.8*

ubuntu/linux-azure*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15<5.15.0-1094.103~20.04.1

5.15.0-1094.103~20.04.1

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-bluefield*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15<5.15.0-1087.96~20.04.2

5.15.0-1087.96~20.04.2

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<5.15.0-144.157~20.04.1

5.15.0-144.157~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm*

ubuntu/linux-ibm-5.15<5.15.0-1080.83~20.04.1

5.15.0-1080.83~20.04.1

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1083.89~20.04.1

5.15.0-1083.89~20.04.1

ubuntu/linux-iot*

ubuntu/linux-kvm*

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-144.157~20.04.1

5.15.0-144.157~20.04.1

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1041.41~20.04.1

5.15.0-1041.41~20.04.1

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.15<5.15.0-1085.91~20.04.3

5.15.0-1085.91~20.04.3

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1083.87~20.04.1

5.15.0-1083.87~20.04.1

ubuntu/linux-riscv-5.8*

ubuntu/linux-xilinx-zynqmp*

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<5.15.0-144.157

5.15.0-144.157

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1088.95

5.15.0-1088.95

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1046.49~22.04.1

6.8.0-1046.49~22.04.1

ubuntu/linux-azure<5.15.0-1094.103

5.15.0-1094.103

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1051.57~22.04.1

6.8.0-1051.57~22.04.1

ubuntu/linux-azure-fde<5.15.0-1094.103.1

5.15.0-1094.103.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1046.53~22.04.1

6.8.0-1046.53~22.04.1

ubuntu/linux-gcp<5.15.0-1087.96

5.15.0-1087.96

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1047.50~22.04.2

6.8.0-1047.50~22.04.2

ubuntu/linux-gke<5.15.0-1085.91

5.15.0-1085.91

ubuntu/linux-gkeop<5.15.0-1070.78

5.15.0-1070.78

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-100.100~22.04.1

6.8.0-100.100~22.04.1

ubuntu/linux-ibm<5.15.0-1080.83

5.15.0-1080.83

ubuntu/linux-ibm-6.8<6.8.0-1044.44~22.04.1

6.8.0-1044.44~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1083.89

5.15.0-1083.89

ubuntu/linux-kvm<5.15.0-1084.89

5.15.0-1084.89

ubuntu/linux-lowlatency<5.15.0-144.157

5.15.0-144.157

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-100.100.1~22.04.1

6.8.0-100.100.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1082.83

5.15.0-1082.83

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1046.49~22.04.1

6.8.0-1046.49~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1041.41

5.15.0-1041.41

ubuntu/linux-nvidia-tegra-igx<5.15.0-1030.30

5.15.0-1030.30

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1085.91

5.15.0-1085.91

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1043.44~22.04.1

6.8.0-1043.44~22.04.1

ubuntu/linux-raspi<5.15.0-1083.86

5.15.0-1083.86

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-100.100~22.04.1

6.8.0-100.100~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1052.56

5.15.0-1052.56

ubuntu/linux-bluefield<5.15.0-1072.74

5.15.0-1072.74

ubuntu/linux-intel-iot-realtime<5.15.0-1081.83

5.15.0-1081.83

ubuntu/linux-realtime<5.15.0-1088.97

5.15.0-1088.97

ubuntu/linux-realtime-6.8<6.8.1-1041.42~22.04.1

6.8.1-1041.42~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1088.95+fips1

5.15.0-1088.95+fips1

ubuntu/linux-azure-fips<5.15.0-1094.103+fips1

5.15.0-1094.103+fips1

ubuntu/linux-fips<5.15.0-144.157+fips1

5.15.0-144.157+fips1

ubuntu/linux-gcp-fips<5.15.0-1087.96+fips1

5.15.0-1087.96+fips1

ubuntu/linux<6.8.0-100.100

6.8.0-100.100

ubuntu/linux-aws<6.8.0-1046.49

6.8.0-1046.49

ubuntu/linux-aws-6.14<6.14.0-1011.11~24.04.1

6.14.0-1011.11~24.04.1

ubuntu/linux-azure<6.8.0-1046.52

6.8.0-1046.52

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-fde<6.8.0-1046.53

6.8.0-1046.53

ubuntu/linux-azure-nvidia<6.8.0-1039.42

6.8.0-1039.42

ubuntu/linux-gcp<6.8.0-1047.50

6.8.0-1047.50

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14<6.14.0-1014.15~24.04.1

6.14.0-1014.15~24.04.1

ubuntu/linux-gke<6.8.0-1043.48

6.8.0-1043.48

ubuntu/linux-gkeop<6.8.0-1030.33

6.8.0-1030.33

ubuntu/linux-hwe-6.11*

ubuntu/linux-ibm<6.8.0-1044.44

6.8.0-1044.44

ubuntu/linux-intel*

ubuntu/linux-lowlatency<6.8.0-100.100.1

6.8.0-100.100.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1046.49

6.8.0-1046.49

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-lowlatency<6.8.0-1046.49.1

6.8.0-1046.49.1

ubuntu/linux-nvidia-tegra<6.8.0-1020.20

6.8.0-1020.20

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14<6.14.0-1010.10

6.14.0-1010.10

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1043.44

6.8.0-1043.44

ubuntu/linux-oracle-6.14<6.14.0-1011.11~24.04.1

6.14.0-1011.11~24.04.1

ubuntu/linux-raspi<6.8.0-1047.51

6.8.0-1047.51

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14<6.14.0-28.28.1~24.04.1

6.14.0-28.28.1~24.04.1

ubuntu/linux-xilinx<6.8.0-1023.24

6.8.0-1023.24

ubuntu/linux-bluefield<6.8.0-1016.20

6.8.0-1016.20

ubuntu/linux-raspi-realtime<6.8.0-2037.38

6.8.0-2037.38

ubuntu/linux-realtime<6.8.1-1041.42

6.8.1-1041.42

ubuntu/linux-realtime-6.14<6.14.0-1010.10~24.04.1

6.14.0-1010.10~24.04.1

ubuntu/linux-aws-fips<6.8.0-1046.49+fips1

6.8.0-1046.49+fips1

ubuntu/linux-azure-fips<6.8.0-1046.52+fips1

6.8.0-1046.52+fips1

ubuntu/linux-fips<6.8.0-100.100+fips1

6.8.0-100.100+fips1

ubuntu/linux-gcp-fips<6.8.0-1047.50+fips1

6.8.0-1047.50+fips1

ubuntu/linux-azure-fde*

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

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Upgrade ubuntu/linux-aws-5.15 to a version that resolves this vulnerability.
Fixed in 5.15.0-1088.95~20.04.1
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Fixed in 5.15.0-1094.103~20.04.1
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Fixed in 5.15.0-1087.96~20.04.2
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Fixed in 5.15.0-144.157~20.04.1
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Fixed in 5.15.0-1080.83~20.04.1
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Fixed in 5.15.0-1083.89~20.04.1
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Fixed in 5.15.0-144.157~20.04.1
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Fixed in 5.15.0-1041.41~20.04.1
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Fixed in 5.15.0-1085.91~20.04.3
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Fixed in 5.15.0-1083.87~20.04.1
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Fixed in 5.15.0-144.157
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Fixed in 5.15.0-1088.95
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Fixed in 6.8.0-1046.49~22.04.1
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Fixed in 5.15.0-1094.103
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Fixed in 6.8.0-1051.57~22.04.1
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Fixed in 5.15.0-1094.103.1
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Fixed in 6.8.0-1046.53~22.04.1
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Fixed in 5.15.0-1087.96
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Fixed in 6.8.0-1047.50~22.04.2
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Fixed in 5.15.0-1085.91
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Fixed in 5.15.0-1070.78
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Fixed in 6.8.0-100.100~22.04.1
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Fixed in 5.15.0-1080.83
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Fixed in 6.8.0-1044.44~22.04.1
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Fixed in 5.15.0-1083.89
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Fixed in 5.15.0-1084.89
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Fixed in 5.15.0-144.157
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Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-100.100.1~22.04.1
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Fixed in 5.15.0-1082.83
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Fixed in 6.8.0-1046.49~22.04.1
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Fixed in 5.15.0-1041.41
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Fixed in 5.15.0-1030.30
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Fixed in 5.15.0-1085.91
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Fixed in 6.8.0-1043.44~22.04.1
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Fixed in 5.15.0-1083.86
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Fixed in 6.8.0-100.100~22.04.1
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Fixed in 5.15.0-1052.56
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Fixed in 5.15.0-1072.74
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Fixed in 5.15.0-1081.83
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Fixed in 5.15.0-1088.97
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Fixed in 6.8.1-1041.42~22.04.1
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Fixed in 5.15.0-1088.95+fips1
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Fixed in 5.15.0-1094.103+fips1
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Fixed in 5.15.0-144.157+fips1
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Fixed in 5.15.0-1087.96+fips1
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Fixed in 6.8.0-100.100
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Fixed in 6.8.0-1046.49
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Fixed in 6.14.0-1011.11~24.04.1
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Fixed in 6.8.0-1046.52
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Fixed in 6.8.0-1046.53
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Fixed in 6.8.0-1039.42
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Fixed in 6.8.0-1047.50
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Fixed in 6.14.0-1014.15~24.04.1
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Fixed in 6.8.0-1043.48
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Fixed in 6.8.0-1030.33
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Fixed in 6.8.0-1044.44
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Fixed in 6.8.0-100.100.1
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Fixed in 6.8.0-1046.49
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Fixed in 6.8.0-1046.49.1
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Fixed in 6.8.0-1020.20
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Fixed in 6.14.0-1010.10
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Fixed in 6.8.0-1043.44
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Fixed in 6.14.0-1011.11~24.04.1
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Fixed in 6.8.0-1047.51
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Fixed in 6.14.0-28.28.1~24.04.1
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Fixed in 6.8.0-1023.24
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Fixed in 6.8.0-1016.20
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Fixed in 6.8.0-2037.38
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Fixed in 6.8.1-1041.42
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Fixed in 6.14.0-1010.10~24.04.1
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Fixed in 6.8.0-1046.49+fips1
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Fixed in 6.8.0-1046.52+fips1
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Fixed in 6.8.0-100.100+fips1
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Fixed in 6.8.0-1047.50+fips1
Compensating control
Change xenbus request lifetime management to keep two krefs on each request: one reference for the caller and one for xenbus_thread. Each reference must call kref_put() when finished, with the final kref_put() freeing the request.

Event History

May 20, 2025

CVE Published

via OSV·04:15 PM

Data Sourced

via OSV·04:15 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which systems are exposed to this issue?

The affected software list includes Ubuntu kernels: linux, linux-aws-fips, linux-azure-fips, linux-fips, linux-gcp-fips, linux-azure, linux-gcp, and linux-oracle. The fault occurs in xenbus request handling, so exposure depends on use of the Xen bus subsystem.

What access does an attacker need to exploit it?

The severity vector specifies local attack access, low attack complexity, low privileges required, and no user interaction. The reported impact is availability only; confidentiality and integrity impacts are listed as none.

What failure should operators look for?

The reported symptom is a kernel NULL pointer dereference in the xenbus_thread call stack, involving __wake_up_common, process_msg, and xenbus_thread. This can occur when a Xenbus request is freed after waking a waiting caller while xenbus_thread still accesses the request.

What change resolves the lifetime race?

The resolution tracks each Xenbus request with two krefs: one held by the caller and one held by xenbus_thread. Each holder releases its reference when finished, and the request is freed only after the final kref_put().

UBUNTU-CVE-2025-37949: Null Pointer Dereference

Affected Software

Remediation

Event History

Frequently Asked Questions

Which systems are exposed to this issue?

What access does an attacker need to exploit it?

What failure should operators look for?

What change resolves the lifetime race?

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Frequently Asked Questions

Which systems are exposed to this issue?

What access does an attacker need to exploit it?

What failure should operators look for?

What change resolves the lifetime race?