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VulnerabilityAwaiting classification

CVE-2025-68341

CRITICAL · 9.8 CVSS v3.1 Published 2025-12-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: veth: reduce XDP no_direct return section to fix race As explain in commit fa349e396e48 ("veth: Fix race with AF_XDP exposing old or uninitialized descriptors") for veth there is a chance after napi_complete_done() that another CPU can manage start another NAPI instance running veth_pool(). For NAPI this is correctly handled as the napi_schedule_prep() check will prevent multiple instances from getting scheduled, but for the remaining code in veth_pool() this can run concurrent with the newly started NAPI instance. The problem/race is that xdp_clear_return_frame_no_direct() isn't designed to be nested. Prior to commit 401cb7dae813 ("net: Reference bpf_redirect_info via task_struct on PREEMPT_RT.") the temporary BPF net context bpf_redirect_info was stored per CPU, where this wasn't an issue. Since this commit the BPF context is stored in 'current' task_struct. When running veth in threaded-NAPI mode, then the kthread becomes the storage area. Now a race exists between two concurrent veth_pool() function calls one exiting NAPI and one running new NAPI, both using the same BPF net context. Race is when another CPU gets within the xdp_set_return_frame_no_direct() section before exiting veth_pool() calls the clear-function xdp_clear_return_frame_no_direct().

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A race condition exists in the Linux kernel's veth driver when running in threaded-NAPI mode with XDP. The issue stems from xdp_clear_return_frame_no_direct() not being designed for nested calls - when one veth_pool() instance exits NAPI while another starts, both concurrent calls share the same BPF net context stored in the task_struct, causing the race condition where xdp_set_return_frame_no_direct() can be entered before the clear-function executes.

MitigationApply the kernel patch that reduces the XDP no_direct return section to prevent the race. Until the kernel is updated, avoid running veth interfaces with XDP in threaded-NAPI mode or implement temporary workarounds such as disabling threaded-NAPI for affected veth devices.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify veth interfaces in use
    Run 'ip link show' or 'ls /sys/class/net/' to list network interfaces, then filter for veth* entries. Also check 'cat /sys/class/net/veth*/type' to confirm device type 1 (ethernet).
    Affected if No veth interfaces exist - the system is not affected.
  2. Check if threaded-NAPI mode is enabled for veth
    Examine '/sys/class/net/<veth>/threaded' for each veth interface. If the file exists and contains '1', threaded-NAPI is enabled. Alternatively, check 'ethtool -k <veth>' for napi-threaded or similar flags.
    Affected if Threaded-NAPI mode is disabled (value is 0 or file does not exist) - the race condition cannot trigger.
  3. Verify if XDP is attached to veth interfaces
    Check for XDP programs using 'ip link show <veth>' looking for 'xdp' in the output, or inspect '/sys/class/net/<veth>/xdp' which shows attached XDP programs when XDP is active.
    Affected if No XDP programs are attached to veth interfaces - the vulnerability is not exploitable.
  4. Confirm kernel version and patch status
    Run 'uname -r' to get the running kernel version. Compare against the kernel version that includes the fix for this race condition. Check if the specific patch commit for CVE-2025-68341 is present in the kernel source if accessible.
    Affected if Kernel version is older than the fixed version and the patch is not applied.

A system is affected only if it runs a vulnerable kernel version, uses veth interfaces with threaded-NAPI mode enabled, and has XDP programs attached to those veth interfaces - all three conditions must be true for the race condition to be exploitable.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the kernel patch that reduces the XDP no_direct return section to prevent the race. Until the kernel is updated, avoid running veth interfaces with XDP in threaded-NAPI mode or implement temporary workarounds such as disabling threaded-NAPI for affected veth devices.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing4.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,540
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-68341 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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