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CVE-2025-21681— openvswitch: fix lockup on tx to unregistering netdev with carrier

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ovs_vport_send函数在设备注销时未正确检查设备是否处于运行状态，导致在尝试发送数据时可能陷入无限循环，锁定核心。

AI Predicted 7.8 Difficulty: Moderate EPSS 0.22% · P12

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 9b0dd09c1ceb35950d2884848099fccc9ec9a123< b5c73fc92f8d15c16e5dc87b5c17d2abf1e6d092 affected
284be5db6c8d06d247ed056cfc448c4f79bbb16c< 87fcf0d137c770e6040ebfdb0abd8e7dd481b504 affected
5efcb301523baacd98a47553d4996e924923114d< 930268823f6bccb697aa5d2047aeffd4a497308c affected
644b3051b06ba465bc7401bfae9b14963cbc8c1c< ea9e990356b7bee95440ba0e6e83cc4d701afaca affected
066b86787fa3d97b7aefb5ac0a99a22dad2d15f8< ea966b6698785fb9cd0fdb867acd91b222e4723f affected
066b86787fa3d97b7aefb5ac0a99a22dad2d15f8< 82f433e8dd0629e16681edf6039d094b5518d8ed affected
066b86787fa3d97b7aefb5ac0a99a22dad2d15f8< 47e55e4b410f7d552e43011baa5be1aab4093990 affected
56252da41426f3d01957456f13caf46ce670ea29 affected
… +8 more rows
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I. Basic Information for CVE-2025-21681

Vulnerability Information
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Vulnerability Title
openvswitch: fix lockup on tx to unregistering netdev with carrier
Source: CVE Program / CVE List V5
Vulnerability Description
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: do_output -> ovs_vport_send -> dev_queue_xmit -> __dev_queue_xmit -> netdev_core_pick_tx -> skb_tx_hash When device is unregistering, the 'dev->real_num_tx_queues' goes to zero and the 'while (unlikely(hash >= qcount))' loop inside the 'skb_tx_hash' 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 .ndo_stop 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 skb_tx_hash() 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 __dev_direct_xmit() check both before attempting to transmit a packet. So, it seems safer to check both flags in OVS as well.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ovs_vport_send函数在设备注销时未正确检查设备是否处于运行状态，导致在尝试发送数据时可能陷入无限循环，锁定核心。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 9b0dd09c1ceb35950d2884848099fccc9ec9a123 ~ b5c73fc92f8d15c16e5dc87b5c17d2abf1e6d092 -
Linux Linux 6.3 -

II. Public POCs for CVE-2025-21681

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III. Intelligence Information for CVE-2025-21681

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Patches & Fixes for CVE-2025-21681 (7)

Same Patch Batch · Linux · 2025-01-31 · 20 CVEs total

CVE-2025-21673 9.8 CRITICAL smb: client: fix double free of TCP_Server_Info::hostname
CVE-2025-21669 7.8 HIGH vsock/virtio: discard packets if the transport changes
CVE-2025-21680 7.8 HIGH pktgen: Avoid out-of-bounds access in get_imix_entries
CVE-2025-21678 7.8 HIGH gtp: Destroy device along with udp socket's netns dismantle.
CVE-2025-21677 7.8 HIGH pfcp: Destroy device along with udp socket's netns dismantle.
CVE-2025-21676 7.5 HIGH net: fec: handle page_pool_dev_alloc_pages error
CVE-2025-21682 7.3 HIGH eth: bnxt: always recalculate features after XDP clearing, fix null-deref
CVE-2025-21675 net/mlx5: Clear port select structure when fail to create
CVE-2025-21674 net/mlx5e: Fix inversion dependency warning while enabling IPsec tunnel
CVE-2025-21679 btrfs: add the missing error handling inside get_canonical_dev_path
CVE-2025-21672 afs: Fix merge preference rule failure condition
CVE-2025-21671 zram: fix potential UAF of zram table
CVE-2025-21670 vsock/bpf: return early if transport is not assigned
CVE-2025-21683 bpf: Fix bpf_sk_select_reuseport() memory leak
CVE-2025-21668 pmdomain: imx8mp-blk-ctrl: add missing loop break condition
CVE-2025-21667 iomap: avoid avoid truncating 64-bit offset to 32 bits
CVE-2025-21666 vsock: prevent null-ptr-deref in vsock_*[has_data|has_space]
CVE-2025-21665 filemap: avoid truncating 64-bit offset to 32 bits
CVE-2024-57948 mac802154: check local interfaces before deleting sdata list

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-21681

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