CVE-2025-40123: bpf: Enforce expected_attach_type for tailcall compatibility

Q: What is the severity of CVE-2025-40123?

CVE-2025-40123 has been classified as a medium severity vulnerability.

Q: How do I fix CVE-2025-40123?

To fix CVE-2025-40123, update to the latest version of the Linux kernel that includes the patch addressing this issue.

Q: What systems are affected by CVE-2025-40123?

CVE-2025-40123 affects various versions of the Linux kernel.

Q: What type of vulnerability is CVE-2025-40123?

CVE-2025-40123 is an uninitialized pointer vulnerability that affects the bpf_prog_test_run_xdp() function.

Q: Is there a known exploit for CVE-2025-40123?

As of now, there have been no public exploits reported for CVE-2025-40123.

Published Nov 12, 2025

Updated

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

bpf: Enforce expectedattachtype for tailcall compatibility

Yinhao et al. recently reported:

Our fuzzer tool discovered an uninitialized pointer issue in the bpfprogtestrunxdp() function within the Linux kernel's BPF subsystem. This leads to a NULL pointer dereference when a BPF program attempts to deference the txq member of struct xdpbuff object.

The test initializes two programs of BPFPROGTYPEXDP: progA acts as the entry point for bpfprogtestrunxdp() and its expectedattachtype can neither be of be BPFXDPDEVMAP nor BPFXDPCPUMAP. progA calls into a slot of a tailcall map it owns. progB's expectedattachtype must be BPFXDPDEVMAP to pass xdpisvalidaccess() validation. The program returns struct xdpmd's egressifindex, and the latter is only allowed to be accessed under mentioned expectedattachtype. progB is then inserted into the tailcall which progA calls.

The underlying issue goes beyond XDP though. Another example are programs of type BPFPROGTYPECGROUPSOCKADDR. sockaddrisvalidaccess() as well as sockaddrfuncproto() have different logic depending on the programs' expectedattachtype. Similarly, a program attached to BPFCGROUPINET4GETPEERNAME should not be allowed doing a tailcall into a program which calls bpfbind() out of BPF which is only enabled for BPFCGROUPINET4CONNECT.

In short, specifying expectedattachtype allows to open up additional functionality or restrictions beyond what the basic bpfprogtype enables. The use of tailcalls must not violate these constraints. Fix it by enforcing expectedattachtype in bpfprogmapcompatible().

Note that we only enforce this for tailcall maps, but not for BPF devmaps or cpumaps: There, the programs are invoked through devmapbpfprogrun() and cpumapbpfprogrun() which set up a new environment / context and therefore these situations are not prone to this issue.

Affected Software

213 affected componentsFixes available

Linux Linux kernel

ubuntu/linux-hwe-edge*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4*

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

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-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4*

ubuntu/linux-raspi-5.4*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1119.126~20.04.1

5.15.0-1119.126~20.04.1

ubuntu/linux-aws-5.8*

ubuntu/linux-azure*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15<5.15.0-1125.134~20.04.1

5.15.0-1125.134~20.04.1

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-azure-fde-5.15<5.15.0-1124.133~20.04.1

5.15.0-1124.133~20.04.1

ubuntu/linux-bluefield*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15<5.15.0-1120.130~20.04.1

5.15.0-1120.130~20.04.1

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<5.15.0-202.212~20.04.1

5.15.0-202.212~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm*

ubuntu/linux-ibm-5.15<5.15.0-1113.117~20.04.1

5.15.0-1113.117~20.04.1

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1114.120~20.04.1

5.15.0-1114.120~20.04.1

ubuntu/linux-iot*

ubuntu/linux-kvm*

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-197.207~20.04.1

5.15.0-197.207~20.04.1

ubuntu/linux-nvidia-tegra-5.15<5.15.0-1070.72~20.04.1

5.15.0-1070.72~20.04.1

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<5.15.0-1116.122~20.04.1

5.15.0-1116.122~20.04.1

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1113.117~20.04.2

5.15.0-1113.117~20.04.2

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<5.15.0-202.212

5.15.0-202.212

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1119.126

5.15.0-1119.126

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1050.53~22.04.1

6.8.0-1050.53~22.04.1

ubuntu/linux-azure<5.15.0-1125.134

5.15.0-1125.134

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<5.15.0-1124.133

5.15.0-1124.133

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1058.65~22.04.1

6.8.0-1058.65~22.04.1

ubuntu/linux-gcp<5.15.0-1120.130

5.15.0-1120.130

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1052.55~22.04.1

6.8.0-1052.55~22.04.1

ubuntu/linux-gke<5.15.0-1115.121

5.15.0-1115.121

ubuntu/linux-gkeop<5.15.0-1102.110

5.15.0-1102.110

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-ibm<5.15.0-1113.117

5.15.0-1113.117

ubuntu/linux-ibm-6.8<6.8.0-1049.49~22.04.1

6.8.0-1049.49~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1114.120

5.15.0-1114.120

ubuntu/linux-kvm<5.15.0-1111.116

5.15.0-1111.116

ubuntu/linux-lowlatency<5.15.0-197.207

5.15.0-197.207

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-106.106.1~22.04.1

6.8.0-106.106.1~22.04.1

ubuntu/linux-nvidia<5.15.0-1114.115

5.15.0-1114.115

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1049.52~22.04.1

6.8.0-1049.52~22.04.1

ubuntu/linux-nvidia-tegra<5.15.0-1070.72

5.15.0-1070.72

ubuntu/linux-nvidia-tegra-igx<5.15.0-1059.59

5.15.0-1059.59

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1116.122

5.15.0-1116.122

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1047.48~22.04.1

6.8.0-1047.48~22.04.1

ubuntu/linux-raspi<5.15.0-1113.116

5.15.0-1113.116

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp*

ubuntu/linux-bluefield<5.15.0-1103.105

5.15.0-1103.105

ubuntu/linux-intel-iot-realtime<5.15.0-1111.115

5.15.0-1111.115

ubuntu/linux-realtime<5.15.0-1118.127

5.15.0-1118.127

ubuntu/linux-realtime-6.8<6.8.1-1045.46~22.04.1

6.8.1-1045.46~22.04.1

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1119.126+fips1

5.15.0-1119.126+fips1

ubuntu/linux-azure-fips<5.15.0-1125.134+fips1

5.15.0-1125.134+fips1

ubuntu/linux-fips<5.15.0-202.212+fips1

5.15.0-202.212+fips1

ubuntu/linux-gcp-fips<5.15.0-1120.130+fips1

5.15.0-1120.130+fips1

ubuntu/linux<6.8.0-106.106

6.8.0-106.106

ubuntu/linux-aws<6.8.0-1050.53

6.8.0-1050.53

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17<6.17.0-1007.7~24.04.1

6.17.0-1007.7~24.04.1

ubuntu/linux-azure<6.8.0-1051.57

6.8.0-1051.57

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-fde<6.8.0-1058.65

6.8.0-1058.65

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-nvidia<6.8.0-1039.42

6.8.0-1039.42

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1052.55

6.8.0-1052.55

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-6.17<6.17.0-1008.8~24.04.1

6.17.0-1008.8~24.04.1

ubuntu/linux-gke<6.8.0-1048.53

6.8.0-1048.53

ubuntu/linux-gkeop<6.8.0-1035.38

6.8.0-1035.38

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-ibm<6.8.0-1049.49

6.8.0-1049.49

ubuntu/linux-lowlatency<6.8.0-106.106.1

6.8.0-106.106.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1049.52

6.8.0-1049.52

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-nvidia-lowlatency<6.8.0-1049.52.1

6.8.0-1049.52.1

ubuntu/linux-nvidia-tegra<6.8.0-1020.20

6.8.0-1020.20

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17<6.17.0-1011.11

6.17.0-1011.11

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1047.48

6.8.0-1047.48

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17<6.17.0-1007.7~24.04.1

6.17.0-1007.7~24.04.1

ubuntu/linux-raspi<6.8.0-1050.54

6.8.0-1050.54

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-xilinx<6.8.0-1028.29

6.8.0-1028.29

ubuntu/linux-bluefield<6.8.0-1017.21

6.8.0-1017.21

ubuntu/linux-raspi-realtime<6.8.0-2040.41

6.8.0-2040.41

ubuntu/linux-realtime<6.8.1-1045.46

6.8.1-1045.46

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17<6.17.0-1006.7~24.04.1

6.17.0-1006.7~24.04.1

ubuntu/linux-aws-fips<6.8.0-1050.53+fips1

6.8.0-1050.53+fips1

ubuntu/linux-azure-fips<6.8.0-1052.58+fips1

6.8.0-1052.58+fips1

ubuntu/linux-fips<6.8.0-106.106+fips1

6.8.0-106.106+fips1

ubuntu/linux-gcp-fips<6.8.0-1052.55+fips1

6.8.0-1052.55+fips1

ubuntu/linux<6.17.0-14.14

6.17.0-14.14

ubuntu/linux-aws<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-azure<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-azure-fde*

ubuntu/linux-gcp<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-oracle<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-raspi<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-realtime<6.17.0-1006.7

6.17.0-1006.7

ubuntu/linux-riscv<6.17.0-14.14.1

6.17.0-14.14.1

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

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Fixed in 5.15.0-1119.126~20.04.1
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Fixed in 5.15.0-1125.134~20.04.1
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Fixed in 5.15.0-1124.133~20.04.1
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Fixed in 5.15.0-1120.130~20.04.1
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Fixed in 5.15.0-202.212~20.04.1
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Fixed in 5.15.0-1113.117~20.04.1
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Fixed in 5.15.0-1114.120~20.04.1
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Fixed in 5.15.0-197.207~20.04.1
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Fixed in 5.15.0-1070.72~20.04.1
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Fixed in 5.15.0-1116.122~20.04.1
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Fixed in 5.15.0-1113.117~20.04.2
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Fixed in 5.15.0-202.212
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Fixed in 5.15.0-1119.126
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Fixed in 6.8.0-1050.53~22.04.1
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Fixed in 5.15.0-1125.134
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Fixed in 6.8.0-1051.57~22.04.1
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Fixed in 5.15.0-1124.133
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Fixed in 6.8.0-1058.65~22.04.1
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Fixed in 5.15.0-1120.130
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Fixed in 6.8.0-1052.55~22.04.1
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Fixed in 5.15.0-1115.121
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Fixed in 5.15.0-1102.110
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Fixed in 6.8.0-106.106~22.04.1
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Fixed in 5.15.0-1113.117
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Fixed in 6.8.0-1049.49~22.04.1
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Fixed in 5.15.0-1114.120
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Fixed in 5.15.0-1111.116
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Fixed in 5.15.0-197.207
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Fixed in 6.8.0-106.106.1~22.04.1
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Fixed in 5.15.0-1114.115
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Fixed in 6.8.0-1049.52~22.04.1
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Fixed in 5.15.0-1111.115
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Fixed in 5.15.0-1118.127
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Fixed in 6.8.1-1045.46~22.04.1
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Fixed in 5.15.0-202.212+fips1
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Fixed in 6.8.0-1050.53
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Fixed in 6.17.0-1007.7~24.04.1
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Fixed in 6.17.0-1008.8~24.04.1
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Fixed in 6.8.0-1048.53
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Fixed in 6.8.0-1035.38
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Fixed in 6.8.0-1049.49
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Fixed in 6.8.0-106.106.1
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Fixed in 6.8.0-1049.52
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Fixed in 6.17.0-1008.8
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Fixed in 6.8.0-1049.52.1
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Fixed in 6.8.0-1020.20
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Fixed in 6.17.0-1011.11
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Fixed in 6.8.0-1047.48
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Fixed in 6.17.0-1007.7~24.04.1
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Fixed in 6.8.0-1050.54
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Fixed in 6.8.0-1028.29
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Fixed in 6.8.0-1017.21
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Fixed in 6.8.0-2040.41
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Fixed in 6.8.1-1045.46
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Fixed in 6.17.0-1006.7~24.04.1
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Fixed in 6.8.0-1050.53+fips1
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Fixed in 6.8.0-1052.58+fips1
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Fixed in 6.8.0-106.106+fips1
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Fixed in 6.8.0-1052.55+fips1
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Fixed in 6.17.0-14.14
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Fixed in 6.17.0-1007.7
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Fixed in 6.17.0-1008.8
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Fixed in 6.17.0-1007.7
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Fixed in 6.17.0-1007.7
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Fixed in 6.17.0-1008.8
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Fixed in 6.17.0-1006.7
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Fixed in 6.17.0-14.14.1

Event History

Nov 12, 2025

CVE Published

via MITRE·10:23 AM

Data Sourced

via MITRE·10:23 AM

DescriptionSeverity

Data Sourced

via OSV·11:15 AM

DescriptionSeverityAffected Software

Data Sourced

via NVD·11:15 AM

DescriptionSeverity

Aug 24, 2026

Exploit Published

via GitHub·03:03 AM

Frequently Asked Questions

What is the severity of CVE-2025-40123?

CVE-2025-40123 has been classified as a medium severity vulnerability.

How do I fix CVE-2025-40123?

To fix CVE-2025-40123, update to the latest version of the Linux kernel that includes the patch addressing this issue.

What systems are affected by CVE-2025-40123?

CVE-2025-40123 affects various versions of the Linux kernel.

What type of vulnerability is CVE-2025-40123?

CVE-2025-40123 is an uninitialized pointer vulnerability that affects the bpf_prog_test_run_xdp() function.

Is there a known exploit for CVE-2025-40123?

As of now, there have been no public exploits reported for CVE-2025-40123.

CVE-2025-40123: bpf: Enforce expected_attach_type for tailcall compatibility

Affected Software

Remediation

Event History

Frequently Asked Questions

What is the severity of CVE-2025-40123?

How do I fix CVE-2025-40123?

What systems are affected by CVE-2025-40123?

What type of vulnerability is CVE-2025-40123?

Is there a known exploit for CVE-2025-40123?

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