UBUNTU-CVE-2025-21681: Medium severity ubuntu/linux-hwe-edge vulnerability

Q: Which systems are most likely to be exposed?

Systems using the Open vSwitch datapath and transmitting packets to a network device while that device is unregistering are exposed. Dummy interfaces are specifically significant because they are frequently used as packet sinks for tcpdump during OVS debugging and can retain carrier status while unregistering.

Q: What conditions are needed to trigger the lockup?

An attacker or local process needs to cause packet transmission through OVS to a device during its unregistering state, when the device has zero transmit queues. If the device still reports carrier as up, skb_tx_hash() can loop indefinitely and lock up a CPU core.

Q: Is checking whether the target interface has carrier enabled sufficient mitigation?

No. Some devices, including net/dummy, may report carrier as enabled while unregistering, so carrier status alone does not prevent the affected path.

Published Jan 31, 2025

Updated

In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix lockup on tx to unregistering netdev with carrier Commit in a fixes tag attempted to fix the issue in the following sequence of calls: dooutput -> ovsvportsend -> devqueuexmit -> devqueuexmit -> netdevcorepicktx -> skbtxhash When device is unregistering, the 'dev->realnumtxqueues' goes to zero and the 'while (unlikely(hash >= qcount))' loop inside the 'skbtxhash' becomes infinite, locking up the core forever. But unfortunately, checking just the carrier status is not enough to fix the issue, because some devices may still be in unregistering state while reporting carrier status OK. One example of such device is a net/dummy. It sets carrier ON on start, but it doesn't implement .ndostop to set the carrier off. And it makes sense, because dummy doesn't really have a carrier. Therefore, while this device is unregistering, it's still easy to hit the infinite loop in the skbtxhash() from the OVS datapath. There might be other drivers that do the same, but dummy by itself is important for the OVS ecosystem, because it is frequently used as a packet sink for tcpdump while debugging OVS deployments. And when the issue is hit, the only way to recover is to reboot. Fix that by also checking if the device is running. The running state is handled by the net core during unregistering, so it covers unregistering case better, and we don't really need to send packets to devices that are not running anyway. While only checking the running state might be enough, the carrier check is preserved. The running and the carrier states seem disjoined throughout the code and different drivers. And other core functions like devdirectxmit() check both before attempting to transmit a packet. So, it seems safer to check both flags in OVS as well.

Affected Software

117 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-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-bluefield*

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-5.8*

ubuntu/linux-intel-5.13*

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-allwinner-5.19*

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1030.32~22.04.1

6.8.0-1030.32~22.04.1

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1030.35~22.04.1

6.8.0-1030.35~22.04.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1031.33~22.04.1

6.8.0-1031.33~22.04.1

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-64.67~22.04.1

6.8.0-64.67~22.04.1

ubuntu/linux-ibm-6.8<6.8.0-1027.27~22.04.1

6.8.0-1027.27~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-62.65.1~22.04.1

6.8.0-62.65.1~22.04.1

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1029.32~22.04.1

6.8.0-1029.32~22.04.1

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1027.28~22.04.1

6.8.0-1027.28~22.04.1

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-62.65~22.04.1

6.8.0-62.65~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-bluefield<5.15.0-1072.74

5.15.0-1072.74

ubuntu/linux-realtime-6.8<6.8.1-1023.24~22.04.1

6.8.1-1023.24~22.04.1

ubuntu/linux<6.8.0-62.65

6.8.0-62.65

ubuntu/linux-aws<6.8.0-1030.32

6.8.0-1030.32

ubuntu/linux-azure<6.8.0-1030.35

6.8.0-1030.35

ubuntu/linux-azure-6.11<6.11.0-1013.13~24.04.1

6.11.0-1013.13~24.04.1

ubuntu/linux-azure-nvidia<6.8.0-1018.19

6.8.0-1018.19

ubuntu/linux-gcp<6.8.0-1031.33

6.8.0-1031.33

ubuntu/linux-gcp-6.11<6.11.0-1013.13~24.04.1

6.11.0-1013.13~24.04.1

ubuntu/linux-gke<6.8.0-1026.30

6.8.0-1026.30

ubuntu/linux-gkeop<6.8.0-1013.15

6.8.0-1013.15

ubuntu/linux-hwe-6.11<6.11.0-24.24~24.04.1

6.11.0-24.24~24.04.1

ubuntu/linux-ibm<6.8.0-1027.27

6.8.0-1027.27

ubuntu/linux-lowlatency<6.8.0-62.65.1

6.8.0-62.65.1

ubuntu/linux-lowlatency-hwe-6.11<6.11.0-1012.13~24.04.1

6.11.0-1012.13~24.04.1

ubuntu/linux-nvidia<6.8.0-1029.32

6.8.0-1029.32

ubuntu/linux-nvidia-6.11<6.11.0-1007.7

6.11.0-1007.7

ubuntu/linux-nvidia-lowlatency<6.8.0-1029.32.1

6.8.0-1029.32.1

ubuntu/linux-nvidia-tegra<6.8.0-1008.8

6.8.0-1008.8

ubuntu/linux-oem-6.11<6.11.0-1020.20

6.11.0-1020.20

ubuntu/linux-oem-6.8<6.8.0-1029.29

6.8.0-1029.29

ubuntu/linux-oracle<6.8.0-1027.28

6.8.0-1027.28

ubuntu/linux-raspi<6.8.0-1029.33

6.8.0-1029.33

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<6.8.0-2024.25

6.8.0-2024.25

ubuntu/linux-realtime<6.8.1-1023.24

6.8.1-1023.24

ubuntu/linux-fips<6.8.0-78.78+fips1

6.8.0-78.78+fips1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1030.32~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1030.35~22.04.1
Upgrade
Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1031.33~22.04.1
Upgrade
Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-64.67~22.04.1
Upgrade
Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1027.27~22.04.1
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-62.65.1~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.32~22.04.1
Upgrade
Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1027.28~22.04.1
Upgrade
Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-62.65~22.04.1
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 5.15.0-1072.74
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1023.24~22.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-62.65
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1030.32
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1030.35
Upgrade
Upgrade ubuntu/linux-azure-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1013.13~24.04.1
Upgrade
Upgrade ubuntu/linux-azure-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1018.19
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.8.0-1031.33
Upgrade
Upgrade ubuntu/linux-gcp-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1013.13~24.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 6.8.0-1026.30
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 6.8.0-1013.15
Upgrade
Upgrade ubuntu/linux-hwe-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-24.24~24.04.1
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 6.8.0-1027.27
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-62.65.1
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1012.13~24.04.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.32
Upgrade
Upgrade ubuntu/linux-nvidia-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1007.7
Upgrade
Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.32.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 6.8.0-1008.8
Upgrade
Upgrade ubuntu/linux-oem-6.11 to a version that resolves this vulnerability.
Fixed in 6.11.0-1020.20
Upgrade
Upgrade ubuntu/linux-oem-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.29
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.8.0-1027.28
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.8.0-1029.33
Upgrade
Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.
Fixed in 6.8.0-1017.18
Upgrade
Upgrade ubuntu/linux-raspi-realtime to a version that resolves this vulnerability.
Fixed in 6.8.0-2024.25
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.8.1-1023.24
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-78.78+fips1
Compensating control
Modify the Open vSwitch transmit path to check that the network device is both running and has carrier before transmitting packets, preserving the carrier check while adding the running-state check.

Event History

Jan 31, 2025

CVE Published

via OSV·12:15 PM

Data Sourced

via OSV·12:15 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which systems are most likely to be exposed?

Systems using the Open vSwitch datapath and transmitting packets to a network device while that device is unregistering are exposed. Dummy interfaces are specifically significant because they are frequently used as packet sinks for tcpdump during OVS debugging and can retain carrier status while unregistering.

What conditions are needed to trigger the lockup?

An attacker or local process needs to cause packet transmission through OVS to a device during its unregistering state, when the device has zero transmit queues. If the device still reports carrier as up, skb_tx_hash() can loop indefinitely and lock up a CPU core.

Is checking whether the target interface has carrier enabled sufficient mitigation?

No. Some devices, including net/dummy, may report carrier as enabled while unregistering, so carrier status alone does not prevent the affected path.

UBUNTU-CVE-2025-21681: Medium severity ubuntu/linux-hwe-edge vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

Which systems are most likely to be exposed?

What conditions are needed to trigger the lockup?

Is checking whether the target interface has carrier enabled sufficient mitigation?

Company

Resources

Contact

Frequently Asked Questions

Which systems are most likely to be exposed?

What conditions are needed to trigger the lockup?

Is checking whether the target interface has carrier enabled sufficient mitigation?