CVE-2023-53188
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-15

Last updated on: 2025-12-02

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: fix race on port output assume the following setup on a single machine: 1. An openvswitch instance with one bridge and default flows 2. two network namespaces "server" and "client" 3. two ovs interfaces "server" and "client" on the bridge 4. for each ovs interface a veth pair with a matching name and 32 rx and tx queues 5. move the ends of the veth pairs to the respective network namespaces 6. assign ip addresses to each of the veth ends in the namespaces (needs to be the same subnet) 7. start some http server on the server network namespace 8. test if a client in the client namespace can reach the http server when following the actions below the host has a chance of getting a cpu stuck in a infinite loop: 1. send a large amount of parallel requests to the http server (around 3000 curls should work) 2. in parallel delete the network namespace (do not delete interfaces or stop the server, just kill the namespace) there is a low chance that this will cause the below kernel cpu stuck message. If this does not happen just retry. Below there is also the output of bpftrace for the functions mentioned in the output. The series of events happening here is: 1. the network namespace is deleted calling `unregister_netdevice_many_notify` somewhere in the process 2. this sets first `NETREG_UNREGISTERING` on both ends of the veth and then runs `synchronize_net` 3. it then calls `call_netdevice_notifiers` with `NETDEV_UNREGISTER` 4. this is then handled by `dp_device_event` which calls `ovs_netdev_detach_dev` (if a vport is found, which is the case for the veth interface attached to ovs) 5. this removes the rx_handlers of the device but does not prevent packages to be sent to the device 6. `dp_device_event` then queues the vport deletion to work in background as a ovs_lock is needed that we do not hold in the unregistration path 7. `unregister_netdevice_many_notify` continues to call `netdev_unregister_kobject` which sets `real_num_tx_queues` to 0 8. port deletion continues (but details are not relevant for this issue) 9. at some future point the background task deletes the vport If after 7. but before 9. a packet is send to the ovs vport (which is not deleted at this point in time) which forwards it to the `dev_queue_xmit` flow even though the device is unregistering. In `skb_tx_hash` (which is called in the `dev_queue_xmit`) path there is a while loop (if the packet has a rx_queue recorded) that is infinite if `dev->real_num_tx_queues` is zero. To prevent this from happening we update `do_output` to handle devices without carrier the same as if the device is not found (which would be the code path after 9. is done). Additionally we now produce a warning in `skb_tx_hash` if we will hit the infinite loop. bpftrace (first word is function name): __dev_queue_xmit server: real_num_tx_queues: 1, cpu: 2, pid: 28024, tid: 28024, skb_addr: 0xffff9edb6f207000, reg_state: 1 netdev_core_pick_tx server: addr: 0xffff9f0a46d4a000 real_num_tx_queues: 1, cpu: 2, pid: 28024, tid: 28024, skb_addr: 0xffff9edb6f207000, reg_state: 1 dp_device_event server: real_num_tx_queues: 1 cpu 9, pid: 21024, tid: 21024, event 2, reg_state: 1 synchronize_rcu_expedited: cpu 9, pid: 21024, tid: 21024 synchronize_rcu_expedited: cpu 9, pid: 21024, tid: 21024 synchronize_rcu_expedited: cpu 9, pid: 21024, tid: 21024 synchronize_rcu_expedited: cpu 9, pid: 21024, tid: 21024 dp_device_event server: real_num_tx_queues: 1 cpu 9, pid: 21024, tid: 21024, event 6, reg_state: 2 ovs_netdev_detach_dev server: real_num_tx_queues: 1 cpu 9, pid: 21024, tid: 21024, reg_state: 2 netdev_rx_handler_unregister server: real_num_tx_queues: 1, cpu: 9, pid: 21024, tid: 21024, reg_state: 2 synchronize_rcu_expedited: cpu 9, pid: 21024, tid: 21024 netdev_rx_handler_unregister ret server: real_num_tx_queues: 1, cpu: 9, pid: 21024, tid: 21024, reg_state: 2 dp_ ---truncated---
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Meta Information
Published
2025-09-15
Last Modified
2025-12-02
Generated
2026-05-07
AI Q&A
2025-09-15
EPSS Evaluated
2026-05-05
NVD
CVE-2023-53188
Affected Vendors & Products
Showing 11 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 4.3 (inc) to 5.4.293 (exc)
linux linux_kernel From 5.5 (inc) to 5.10.237 (exc)
linux linux_kernel From 5.11 (inc) to 5.15.181 (exc)
linux linux_kernel From 5.16 (inc) to 6.1.25 (exc)
linux linux_kernel From 6.2 (inc) to 6.2.12 (exc)
linux linux_kernel 6.3
linux linux_kernel 6.3
linux linux_kernel 6.3
linux linux_kernel 6.3
linux linux_kernel 6.3
linux linux_kernel 6.3
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-362 The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a race condition in the Linux kernel's openvswitch networking component. It occurs when a network namespace is deleted while many parallel requests are sent to an HTTP server running in that namespace. During this process, the kernel may enter an infinite loop in the packet transmission code because the device's transmit queues are set to zero but packets are still forwarded to it. This can cause the CPU to get stuck, leading to a system hang or degraded performance.


How can this vulnerability impact me? :

The vulnerability can cause the host system's CPU to become stuck in an infinite loop, effectively hanging or severely degrading the performance of the system. This can disrupt network communication and services relying on openvswitch, potentially causing denial of service or instability in environments using network namespaces and openvswitch.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by reproducing the described conditions: setting up an Open vSwitch instance with network namespaces and veth pairs, then sending a large number of parallel requests (around 3000 curls) to a server in one namespace while deleting the other namespace in parallel. Detection involves observing if the host CPU gets stuck in an infinite loop, which may manifest as kernel CPU stuck messages. Specific commands include using curl to send parallel requests and monitoring kernel logs for CPU stuck warnings. However, no explicit detection commands are provided.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where the vulnerability is fixed. The fix updates the do_output function to handle devices without carrier properly and adds warnings to prevent infinite loops. Until the patch is applied, avoid deleting network namespaces while sending large parallel requests through Open vSwitch interfaces to prevent triggering the issue.


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