EUVD-2026-64371
GHSA-23q4-679m-qgxw
Severity by source
AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Controlling a guest VM or tap device requires at minimum low user-level access on or to the host, making PR:N an overstatement; all other metrics from the provided vector are appropriate.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp()
The commit 4f61f133f354 ("net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null") fixed a crash in tap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb(). This is required because virtio_net_hdr_to_skb() may invoke dev_parse_header_protocol(), which dereferences skb->dev. Without the assignment, a NULL pointer dereference can occur.
However, tap_get_user_xdp() still parses the virtio-net header before assigning skb->dev. When the vhost TX path passes an XDP buffer containing a GSO virtio-net header but the protocol is set to zero on purpose, tun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev is still NULL, resulting in a crash.
Fix this by looking up the tap device and assigning skb->dev before calling tun_vnet_hdr_to_skb(), matching the ordering already used in tap_get_user(). Preserve the existing RCU read-side critical section across dev_queue_xmit().
AnalysisAI
NULL pointer dereference in the Linux kernel's tap_get_user_xdp() function can be triggered by a local attacker or malicious guest VM to crash the host kernel. The flaw arises because skb->dev is not assigned before tun_vnet_hdr_to_skb() is called in the XDP path, while the parallel code path tap_get_user() had already received a fix for the identical ordering defect. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a system actively running the Linux kernel's vhost/virtio-net stack with tap driver XDP processing - the configuration typical of QEMU/KVM virtualization hosts using vhost-net for guest network acceleration. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 7.1 (AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) reflects a locally-triggered, high-availability-impact flaw with a changed scope - the scope change is appropriate because a guest VM's crafted transmit triggers a crash on the host kernel. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An adversary controlling a guest VM connected to the host via a vhost-net tap device crafts an XDP buffer whose virtio-net header includes GSO flags but sets the protocol field to zero. When the guest transmits this buffer, the host kernel's vhost TX path invokes tap_get_user_xdp(), which calls tun_vnet_hdr_to_skb() before skb->dev is assigned; dev_parse_header_protocol() then dereferences the NULL skb->dev pointer, causing the host kernel to panic and all hosted VMs to lose availability. … |
| Remediation | Apply the upstream stable kernel fix corresponding to your branch: patches are available at https://git.kernel.org/stable/c/8b444b126cd8e4473e652f529753ed4dd1360a9c, https://git.kernel.org/stable/c/164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b, and https://git.kernel.org/stable/c/3874892dd27d5387aa9a06f58d9060f18f351d24. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Linux systems running kernels with tap driver support, prioritizing hypervisors and container platforms hosting guest workloads. …
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Same technique Denial Of Service
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External POC / Exploit Code
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