---
id: "CVE-2026-99062"
kind: "vulnerability"
aliases: ["CVE-2026-99062"]
title: "Linux kernel: vsock read accounting bug breaks socket readiness reporting"
severity: "unknown"
cvss: null
epss: 0.00209
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["kernel", "linux", "runtime", "virtio", "vsock"]
not_affected_if: ["no-sk-skb-verdict", "no-vsock-use"]
published_at: "2026-10-23T13:17:30+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99062", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-99062", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel: vsock read accounting bug breaks socket readiness reporting

A bug in the Linux kernel's virtio vsock receive path subtracts the wrong byte count after a partial read, so the socket's pending-byte counter underflows. The sources describe wrong SIOCINQ values, false readable polls, and hidden queued data, with no sign of memory corruption or code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update to a Linux kernel release that includes the upstream fix for 'vsock/virtio: account only unread bytes in read_skb()'; the sources do not name version numbers.

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99062
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-99062

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

vsock/virtio: account only unread bytes in read_skb()

After a partial stream receive, rx_bytes tracks the unread suffix while
buf_used and peer credit still cover the whole packet.
virtio_transport_read_skb() dequeues that packet but passes pkt_len for
both counters, underflowing rx_bytes.

On a connected CID_LOCAL stream with an SK_SKB verdict, a 40-byte read
from a 100-byte packet made SIOCINQ report -40, an empty recv return
ELOOP, and poll report the empty socket readable.  After verdict detach,
receiving 40 bytes wrapped the counter to zero and hid those queued bytes
until one more byte arrived.  The fixed run kept the counter balanced
and exposed all queued data immediately.

This was found during an LLM-assisted manual source audit of VSOCK
receive accounting while re-evaluating virtio_transport_read_skb() after
CVE-2024-50169.

Subtract only skb->len minus the VSOCK offset from rx_bytes.  Retain the
full packet length for buf_used and peer credit.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_