CVE-2026-80844: xfrm: ah6: validate routing header segments_left

Q: What conditions are required to trigger the out-of-bounds access?

An attacker needs to supply a raw IPv6 HDRINCL packet containing a routing header whose segments_left value exceeds the number of addresses represented by its hdrlen field. The described example uses hdrlen 2, which describes one address, with segments_left set to 255.

Q: Which traffic path is affected?

The issue is in AH6 processing for IPv6 routing headers, including both input verification and output computation paths. Malformed routing-header errors are propagated to the existing AH6 input and output error paths by the fix.

Q: What happens if a malformed packet is processed by a vulnerable kernel?

The routing-header address pointer can be moved backwards by thousands of bytes and passed to memmove() with a corresponding oversized length. This results in an out-of-bounds memory access.

Q: How can exposure be reduced if the fix cannot be deployed immediately?

The provided information identifies raw IPv6 HDRINCL packets with malformed routing headers as the trigger. Reducing acceptance or generation of such packets, particularly where AH6 processing is used, can reduce exposure; no specific configuration mitigation is provided.

Published Sep 4, 2026

Updated

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

xfrm: ah6: validate routing header segmentsleft

AH6 rearranges routing-header addresses before computing or verifying the ICV. ipv6rearrangerthdr() assumes that segmentsleft is not larger than the number of addresses described by the routing header's hdrlen field.

That assumption does not hold for raw IPv6 HDRINCL packets. A packet with hdrlen equal to 2 describes one address, but can carry an arbitrary segmentsleft value. With segmentsleft equal to 255, the function moves its address pointer 4,064 bytes backwards and passes a 4,064-byte length to memmove(), resulting in an out-of-bounds access.

Validate the invariant locally before modifying the routing header or performing any address-pointer arithmetic, and propagate malformed-header errors to the existing AH6 input and output error paths.

Affected Software

271 affected componentsFixes available

Linux Linux kernel

Microsoft azl3 kernel 6.6.152.1-1<6.6.157.1-1

6.6.157.1-1

debian/linux<6.1.187-1

6.1.187-1

debian/linux<6.12.111-1

6.12.111-1

debian/linux<7.1.13-1

7.1.13-1

debian/linux-6.12<6.12.111-1~deb12u1

6.12.111-1~deb12u1

linux/kernel>=2.6.12<5.10.269

5.10.269

linux/kernel>=5.11.0<5.15.220

5.15.220

linux/kernel>=5.16.0<6.1.187

6.1.187

linux/kernel>=6.2.0<6.6.156

6.6.156

linux/kernel>=6.7.0<6.12.108

6.12.108

linux/kernel>=6.13.0<6.18.49

6.18.49

linux/kernel>=6.19.0<7.1.13

7.1.13

linux/kernel>=7.2.0<7.2.3

7.2.3

debian/linux<=6.1.176-1, <=6.12.107-1

6.1.190-16.12.116-17.2.15-17.3.4-1

debian/linux-6.12

6.12.115-2~deb12u1

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-azure*

ubuntu/linux-lts-xenial*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-hwe*

ubuntu/linux-azure*

ubuntu/linux-gcp*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-kvm*

ubuntu/linux-oracle*

ubuntu/linux-fips*

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<5.15.0-1119.126~20.04.1

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<6.8.0-1069.74~22.04.1

6.8.0-1069.74~22.04.1

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<6.8.0-1073.82~22.04.1

6.8.0-1073.82~22.04.1

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<6.8.0-1071.78~22.04.1

6.8.0-1071.78~22.04.1

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<6.8.0-1073.81~22.04.1

6.8.0-1073.81~22.04.1

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<6.8.0-149.149~22.04.1

6.8.0-149.149~22.04.1

ubuntu/linux-ibm<5.15.0-1113.117

5.15.0-1113.117

ubuntu/linux-ibm-6.8<6.8.0-1069.70~22.04.1

6.8.0-1069.70~22.04.1

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<6.8.0-149.149.1~22.04.1

6.8.0-149.149.1~22.04.1

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*

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<6.8.0-1067.71~22.04.1

6.8.0-1067.71~22.04.1

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-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<6.8.1-1064.65~22.04.1

6.8.1-1064.65~22.04.1

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<6.8.0-149.149

6.8.0-149.149

ubuntu/linux-aws<6.8.0-1069.74

6.8.0-1069.74

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17*

ubuntu/linux-aws-7.0<7.0.0-1017.18~24.04.1

7.0.0-1017.18~24.04.1

ubuntu/linux-azure<6.8.0-1073.82

6.8.0-1073.82

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-6.17*

ubuntu/linux-azure-7.0*

ubuntu/linux-azure-fde<6.8.0-1071.78

6.8.0-1071.78

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-fde-6.17*

ubuntu/linux-azure-fde-7.0<7.0.0-1019.19~24.04.1

7.0.0-1019.19~24.04.1

ubuntu/linux-azure-nvidia*

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1073.81

6.8.0-1073.81

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-7.0<7.0.0-1017.19~24.04.1

7.0.0-1017.19~24.04.1

ubuntu/linux-gke<6.8.0-1068.77

6.8.0-1068.77

ubuntu/linux-gkeop<6.8.0-1053.57

6.8.0-1053.57

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-hwe-6.17*

ubuntu/linux-hwe-7.0<7.0.0-42.42~24.04.1

7.0.0-42.42~24.04.1

ubuntu/linux-ibm<6.8.0-1069.70

6.8.0-1069.70

ubuntu/linux-lowlatency<6.8.0-149.149.1

6.8.0-149.149.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1067.70

6.8.0-1067.70

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17*

ubuntu/linux-nvidia-7.0*

ubuntu/linux-nvidia-lowlatency<6.8.0-1067.70.1

6.8.0-1067.70.1

ubuntu/linux-nvidia-tegra*

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17*

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1067.71

6.8.0-1067.71

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17*

ubuntu/linux-oracle-7.0<7.0.0-1016.18~24.04.1

7.0.0-1016.18~24.04.1

ubuntu/linux-raspi<6.8.0-1068.72

6.8.0-1068.72

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<7.0.0-42.42.1~24.04.1

7.0.0-42.42.1~24.04.1

ubuntu/linux-vmware<6.8.0-1010.10

6.8.0-1010.10

ubuntu/linux-xilinx*

ubuntu/linux-bluefield<6.8.0-1036.41

6.8.0-1036.41

ubuntu/linux-raspi-realtime<6.8.0-2056.58

6.8.0-2056.58

ubuntu/linux-realtime<6.8.1-1064.65

6.8.1-1064.65

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17*

ubuntu/linux-aws-fips<6.8.0-1069.74+fips1

6.8.0-1069.74+fips1

ubuntu/linux-azure-fips<6.8.0-1073.82+fips1

6.8.0-1073.82+fips1

ubuntu/linux-fips*

ubuntu/linux-gcp-fips<6.8.0-1073.81+fips1

6.8.0-1073.81+fips1

ubuntu/linux<7.0.0-42.42

7.0.0-42.42

ubuntu/linux-aws<7.0.0-1016.17

7.0.0-1016.17

ubuntu/linux-azure<7.0.0-1020.21

7.0.0-1020.21

ubuntu/linux-azure-fde<7.0.0-1019.19

7.0.0-1019.19

ubuntu/linux-gcp<7.0.0-1016.18

7.0.0-1016.18

ubuntu/linux-gke<7.0.0-1010.11

7.0.0-1010.11

ubuntu/linux-ibm<7.0.0-1017.17

7.0.0-1017.17

ubuntu/linux-nvidia*

ubuntu/linux-nvidia-bos*

ubuntu/linux-oem-7.0<7.0.0-1017.17

7.0.0-1017.17

ubuntu/linux-oracle<7.0.0-1015.16

7.0.0-1015.16

ubuntu/linux-raspi<7.0.0-1023.23

7.0.0-1023.23

ubuntu/linux-realtime<7.0.0-43.43.1

7.0.0-43.43.1

ubuntu/linux-riscv<7.0.0-42.42.1

7.0.0-42.42.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

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Fixed in 6.6.157.1-1
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Fixed in 6.1.187-1
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Fixed in 6.12.111-1
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Fixed in 7.1.13-1
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Fixed in 6.12.111-1~deb12u1
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Fixed in 5.10.269
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Fixed in 5.15.220
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Fixed in 6.1.187
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Fixed in 6.6.156
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Fixed in 6.12.108
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Fixed in 6.18.49
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Fixed in 7.1.13
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Fixed in 7.2.3
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Fixed in 6.1.190-1Fixed in 6.12.116-1Fixed in 7.2.15-1Fixed in 7.3.4-1
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Fixed in 6.12.115-2~deb12u1
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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 5.15.0-1116.122~20.04.1
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Fixed in 5.15.0-1113.117
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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 5.15.0-1114.115
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Fixed in 5.15.0-1070.72
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Fixed in 5.15.0-1059.59
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Fixed in 5.15.0-1116.122
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Fixed in 6.8.0-1067.71~22.04.1
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Fixed in 5.15.0-1113.116
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Fixed in 5.15.0-1103.105
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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 6.8.1-1064.65~22.04.1
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Fixed in 5.15.0-1119.126+fips1
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Fixed in 5.15.0-1125.134+fips1
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Fixed in 5.15.0-202.212+fips1
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Fixed in 5.15.0-1120.130+fips1
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Fixed in 6.8.0-149.149
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Fixed in 6.8.0-1069.74
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Fixed in 7.0.0-1017.18~24.04.1
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Fixed in 6.8.0-1073.82
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Fixed in 6.8.0-1071.78
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Fixed in 7.0.0-1019.19~24.04.1
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Fixed in 6.8.0-1073.81
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Fixed in 7.0.0-1017.19~24.04.1
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Fixed in 6.8.0-1068.77
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Fixed in 6.8.0-1053.57
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Fixed in 7.0.0-42.42~24.04.1
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Fixed in 6.8.0-1069.70
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Fixed in 6.8.0-149.149.1
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Fixed in 6.8.0-1067.70
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Fixed in 6.8.0-1067.70.1
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Fixed in 6.8.0-1067.71
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Fixed in 7.0.0-1016.18~24.04.1
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Fixed in 6.8.0-1068.72
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Fixed in 7.0.0-42.42.1~24.04.1
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Fixed in 6.8.0-1010.10
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Fixed in 6.8.0-1036.41
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Fixed in 6.8.0-2056.58
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Fixed in 6.8.1-1064.65
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Fixed in 6.8.0-1069.74+fips1
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Fixed in 6.8.0-1073.82+fips1
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Fixed in 6.8.0-1073.81+fips1
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Fixed in 7.0.0-42.42
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Fixed in 7.0.0-1016.17
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Fixed in 7.0.0-1020.21
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Fixed in 7.0.0-1019.19
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Fixed in 7.0.0-1016.18
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Fixed in 7.0.0-1010.11
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Fixed in 7.0.0-1017.17
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Fixed in 7.0.0-1017.17
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Fixed in 7.0.0-1015.16
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Fixed in 7.0.0-1023.23
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Fixed in 7.0.0-43.43.1
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Fixed in 7.0.0-42.42.1

Event History

Sep 4, 2026

CVE Published

via MITRE·03:54 PM

Data Sourced

via MITRE·03:54 PM

Description

Data Sourced

via OSV·03:54 PM

DescriptionAffected Software

Event

via OSV·04:18 PM

Data Sourced

via NVD·04:18 PM

Description

Data Sourced

via Red Hat·04:23 PM

DescriptionSeverityAffected Software

Sep 6, 2026

Data Sourced

via Microsoft·11:36 AM

DescriptionSeverityWeaknessAffected Software

Sep 18, 2026

Exploit Published

via GitHub·10:07 AM

Nov 12, 2026

Data Sourced

via OSV·11:58 PM

Severity

Parent advisories

This vulnerability appears in the following advisories.

DSA-6528

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

What conditions are required to trigger the out-of-bounds access?

An attacker needs to supply a raw IPv6 HDRINCL packet containing a routing header whose segments_left value exceeds the number of addresses represented by its hdrlen field. The described example uses hdrlen 2, which describes one address, with segments_left set to 255.

Which traffic path is affected?

The issue is in AH6 processing for IPv6 routing headers, including both input verification and output computation paths. Malformed routing-header errors are propagated to the existing AH6 input and output error paths by the fix.

What happens if a malformed packet is processed by a vulnerable kernel?

The routing-header address pointer can be moved backwards by thousands of bytes and passed to memmove() with a corresponding oversized length. This results in an out-of-bounds memory access.

How can exposure be reduced if the fix cannot be deployed immediately?

The provided information identifies raw IPv6 HDRINCL packets with malformed routing headers as the trigger. Reducing acceptance or generation of such packets, particularly where AH6 processing is used, can reduce exposure; no specific configuration mitigation is provided.

CVE-2026-80844: xfrm: ah6: validate routing header segments_left

Affected Software

Remediation

Event History

Parent advisories

Peer vulnerabilities

Frequently Asked Questions

What conditions are required to trigger the out-of-bounds access?

Which traffic path is affected?

What happens if a malformed packet is processed by a vulnerable kernel?

How can exposure be reduced if the fix cannot be deployed immediately?

Company

Resources

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