UBUNTU-CVE-2026-68431: Critical severity ubuntu/linux-hwe-edge vulnerability

Published Aug 12, 2026
·
Updated

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate minimum PDU size for transform requests The receive path applies the minimum SMB2 PDU size check only when ProtocolId is SMB2PROTONUMBER. A packet carrying SMB2TRANSFORMPROTONUM bypasses the check even when the negotiated dialect does not provide transform handling. On an SMB 2.1 connection, a short transform packet therefore reaches initsmb2rsphdr(), which interprets the request as a full SMB2 header and reads beyond the request allocation. The copied fields can then be returned to the unauthenticated client. Compression transforms are converted to ordinary SMB2 messages before protocol validation. After that conversion, validate ordinary SMB2 requests against SMB2MINSUPPORTEDPDUSIZE and require encryption transform requests to contain both a transform header and an SMB2 header. This rejects truncated requests before work allocation.

Affected Software

196 affected componentsFixes available
ubuntu/linux-hwe-edge*
ubuntu/linux-aws-5.0*
ubuntu/linux-aws-5.3*
ubuntu/linux-azure*
ubuntu/linux-azure-5.3*
ubuntu/linux-azure-edge*
ubuntu/linux-gcp*
ubuntu/linux-gcp-5.3*
ubuntu/linux-gke-4.15*
ubuntu/linux-gke-5.4*
ubuntu/linux-gkeop-5.4*
ubuntu/linux-hwe*
ubuntu/linux-hwe-edge*
ubuntu/linux-oem*
ubuntu/linux-oracle-5.0*
ubuntu/linux-oracle-5.3*
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-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-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-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-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-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-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<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*
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*
ubuntu/linux-azure-fde*
ubuntu/linux-azure-fde-5.19*
ubuntu/linux-azure-fde-6.2*
ubuntu/linux-azure-fde-6.8*
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*
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-ibm<5.15.0-1113.117
5.15.0-1113.117
ubuntu/linux-ibm-6.8*
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*
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*
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*
ubuntu/linux-raspi*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.19*
ubuntu/linux-riscv-6.5*
ubuntu/linux-riscv-6.8*
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*
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*
ubuntu/linux-aws*
ubuntu/linux-aws-6.14*
ubuntu/linux-aws-6.17*
ubuntu/linux-aws-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-azure*
ubuntu/linux-azure-6.11*
ubuntu/linux-azure-6.14*
ubuntu/linux-azure-6.17*
ubuntu/linux-azure-7.0<7.0.0-1017.17~24.04.1
7.0.0-1017.17~24.04.1
ubuntu/linux-azure-fde*
ubuntu/linux-azure-fde-6.14*
ubuntu/linux-azure-fde-6.17*
ubuntu/linux-azure-fde-7.0<7.0.0-1016.16~24.04.1
7.0.0-1016.16~24.04.1
ubuntu/linux-azure-nvidia*
ubuntu/linux-azure-nvidia-6.14*
ubuntu/linux-gcp*
ubuntu/linux-gcp-6.11*
ubuntu/linux-gcp-6.14*
ubuntu/linux-gcp-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-gke*
ubuntu/linux-gkeop*
ubuntu/linux-hwe-6.11*
ubuntu/linux-hwe-6.14*
ubuntu/linux-hwe-6.17*
ubuntu/linux-hwe-7.0<7.0.0-38.38~24.04.4
7.0.0-38.38~24.04.4
ubuntu/linux-ibm*
ubuntu/linux-lowlatency*
ubuntu/linux-lowlatency-hwe-6.11*
ubuntu/linux-nvidia*
ubuntu/linux-nvidia-6.11*
ubuntu/linux-nvidia-6.17*
ubuntu/linux-nvidia-7.0*
ubuntu/linux-nvidia-lowlatency*
ubuntu/linux-nvidia-tegra<6.8.0-1035.38
6.8.0-1035.38
ubuntu/linux-oem-6.11*
ubuntu/linux-oem-6.14*
ubuntu/linux-oem-6.17*
ubuntu/linux-oem-6.8*
ubuntu/linux-oracle*
ubuntu/linux-oracle-6.14*
ubuntu/linux-oracle-6.17*
ubuntu/linux-oracle-7.0<7.0.0-1013.13~24.04.1
7.0.0-1013.13~24.04.1
ubuntu/linux-raspi*
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-6.14*
ubuntu/linux-riscv-6.17*
ubuntu/linux-riscv-7.0<7.0.0-38.38.1~24.04.1
7.0.0-38.38.1~24.04.1
ubuntu/linux-xilinx*
ubuntu/linux-bluefield*
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime*
ubuntu/linux-realtime-6.14*
ubuntu/linux-realtime-6.17*
ubuntu/linux-aws-fips*
ubuntu/linux-azure-fips*
ubuntu/linux-fips*
ubuntu/linux-gcp-fips*
ubuntu/linux<7.0.0-38.38
7.0.0-38.38
ubuntu/linux-aws<7.0.0-1014.14
7.0.0-1014.14
ubuntu/linux-azure<7.0.0-1017.17
7.0.0-1017.17
ubuntu/linux-azure-fde<7.0.0-1016.16
7.0.0-1016.16
ubuntu/linux-gcp<7.0.0-1014.14
7.0.0-1014.14
ubuntu/linux-gke<7.0.0-1008.9
7.0.0-1008.9
ubuntu/linux-ibm<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-nvidia*
ubuntu/linux-nvidia-bos*
ubuntu/linux-oem-7.0<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-oracle<7.0.0-1013.13
7.0.0-1013.13
ubuntu/linux-raspi*
ubuntu/linux-realtime<7.0.0-38.38.1
7.0.0-38.38.1
ubuntu/linux-riscv<7.0.0-38.38.1
7.0.0-38.38.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade ubuntu/linux-aws-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1119.126~20.04.1
  2. Upgrade

    Upgrade ubuntu/linux-azure-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1125.134~20.04.1
  3. Upgrade

    Upgrade ubuntu/linux-azure-fde-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1124.133~20.04.1
  4. Upgrade

    Upgrade ubuntu/linux-gcp-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1120.130~20.04.1
  5. Upgrade

    Upgrade ubuntu/linux-hwe-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-202.212~20.04.1
  6. Upgrade

    Upgrade ubuntu/linux-ibm-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1113.117~20.04.1
  7. Upgrade

    Upgrade ubuntu/linux-intel-iotg-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1114.120~20.04.1
  8. Upgrade

    Upgrade ubuntu/linux-lowlatency-hwe-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-197.207~20.04.1
  9. Upgrade

    Upgrade ubuntu/linux-nvidia-tegra-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1070.72~20.04.1
  10. Upgrade

    Upgrade ubuntu/linux-oracle-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1116.122~20.04.1
  11. Upgrade

    Upgrade ubuntu/linux-riscv-5.15 to a version that resolves this vulnerability.

    Fixed in 5.15.0-1113.117~20.04.2
  12. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 5.15.0-202.212
  13. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 5.15.0-1119.126
  14. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 5.15.0-1125.134
  15. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 5.15.0-1120.130
  16. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 5.15.0-1115.121
  17. Upgrade

    Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.

    Fixed in 5.15.0-1102.110
  18. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 5.15.0-1113.117
  19. Upgrade

    Upgrade ubuntu/linux-intel-iotg to a version that resolves this vulnerability.

    Fixed in 5.15.0-1114.120
  20. Upgrade

    Upgrade ubuntu/linux-kvm to a version that resolves this vulnerability.

    Fixed in 5.15.0-1111.116
  21. Upgrade

    Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.

    Fixed in 5.15.0-197.207
  22. Upgrade

    Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.

    Fixed in 5.15.0-1114.115
  23. Upgrade

    Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.

    Fixed in 5.15.0-1070.72
  24. Upgrade

    Upgrade ubuntu/linux-nvidia-tegra-igx to a version that resolves this vulnerability.

    Fixed in 5.15.0-1059.59
  25. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 5.15.0-1116.122
  26. Upgrade

    Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.

    Fixed in 5.15.0-1103.105
  27. Upgrade

    Upgrade ubuntu/linux-intel-iot-realtime to a version that resolves this vulnerability.

    Fixed in 5.15.0-1111.115
  28. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 5.15.0-1118.127
  29. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 5.15.0-1119.126+fips1
  30. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 5.15.0-1125.134+fips1
  31. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 5.15.0-202.212+fips1
  32. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 5.15.0-1120.130+fips1
  33. Upgrade

    Upgrade ubuntu/linux-aws-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  34. Upgrade

    Upgrade ubuntu/linux-azure-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1017.17~24.04.1
  35. Upgrade

    Upgrade ubuntu/linux-azure-fde-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16~24.04.1
  36. Upgrade

    Upgrade ubuntu/linux-gcp-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  37. Upgrade

    Upgrade ubuntu/linux-hwe-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38~24.04.4
  38. Upgrade

    Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.

    Fixed in 6.8.0-1035.38
  39. Upgrade

    Upgrade ubuntu/linux-oracle-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13~24.04.1
  40. Upgrade

    Upgrade ubuntu/linux-riscv-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1~24.04.1
  41. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38
  42. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14
  43. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 7.0.0-1017.17
  44. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16
  45. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14
  46. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 7.0.0-1008.9
  47. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  48. Upgrade

    Upgrade ubuntu/linux-oem-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  49. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13
  50. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1
  51. Upgrade

    Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1
  52. Compensating control

    In the SMB2 receive path, convert compression transforms to ordinary SMB2 messages before protocol validation; then validate ordinary SMB2 requests against SMB2_MIN_SUPPORTED_PDU_SIZE and require encryption transform requests to contain both a transform header and an SMB2 header before work allocation.

Event History

Aug 12, 2026
CVE Published
via OSV·12:17 AM
Data Sourced
via OSV·12:17 AM
DescriptionSeverityAffected Software

Frequently Asked Questions

1

Which systems are exposed to this issue?

Systems running an affected Ubuntu Linux kernel variant listed in the advisory are potentially exposed if ksmbd accepts SMB connections. The vulnerable path is reachable on an SMB 2.1 connection.

2

Does exploitation require authentication or user interaction?

No. The CVSS vector indicates network reachability with low attack complexity, no privileges required, and no user interaction. An unauthenticated client can send the malformed request.

3

What is the impact of a successful exploit?

A truncated transform packet can cause the kernel to read beyond the request allocation, and copied fields may be returned to the unauthenticated client. The supplied severity data also rates availability impact as high.

4

What protocol conditions are involved?

The issue involves short SMB2 transform packets that bypass the normal minimum SMB2 PDU-size check. In particular, a short transform packet on an SMB 2.1 connection can reach SMB2 response-header processing without containing a full SMB2 header.

5

What validation does the fix add?

The fix validates ordinary SMB2 requests against SMB2_MIN_SUPPORTED_PDU_SIZE after compression-transform conversion. It also requires encryption transform requests to include both a transform header and an SMB2 header, rejecting truncated requests before work allocation.

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