---
id: "CVE-2026-99264"
kind: "vulnerability"
aliases: ["CVE-2026-99264"]
title: "Linux kernel: io_uring receive retries can hand out the same buffer twice"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["io_uring", "kernel", "linux", "runtime", "self-hosted"]
not_affected_if: ["default-config", "no-io-uring"]
published_at: "2026-11-03T12:17:33+00:00"
first_seen_at: "2026-11-03T12:20:40+00:00"
updated_at: "2026-11-03T12:22:43+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99264", "first_seen_at": "2026-11-03T12:20:40+00:00"}]
---

# Linux kernel: io_uring receive retries can hand out the same buffer twice

In the Linux kernel's io_uring receive path, a partially completed receive could be retried on ring buffers that were not fully committed, so another request may be given memory the retried receive still writes to. The result is that buffer contents can be overwritten and data from one request may be corrupted or mixed with another's.

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

## How to check

- Check the running kernel version with `uname -r` and compare it against the fixed kernel releases in the sources.
- Look for applications that use io_uring receive operations with incremental provided buffer rings (IOU_PBUF_RING_INC) or multi-buffer bundles.

## Timeline

- 2026-11-03T12:20:40+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99264

## From the sources

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

io_uring/net: don't retry recv on uncommitted buffers

Commit 41b70df5b38b ("io_uring/net: commit partial buffers on retry")
commits ring provided buffers when a receive is going to be retried after
a partial transfer, so that another request using the same buffer group
can't be handed the memory the first one keeps receiving into. It commits
the number of bytes received so far. That does the job for a single
buffer which is consumed as a whole, but the request hangs on to all it
has mapped:

- For a buffer ring with IOU_PBUF_RING_INC only these bytes are consumed.
  The rest of the buffer stays at the head of the ring.
- For a bundle only the buffers which hold these bytes are consumed, the
  others that were peeked stay in the ring.

In both cases the next receive with that buffer group gets memory that
the retried request is still going to write to, and whoever comes last
overwrites the data of the other. What the retry fills isn't committed at
all, as the buffer list isn't known any more at that point. So the kernel
hands it out again later on, while the CQE tells the application that it
was used, and for an incremental buffer that it is done with.

The remainder can't be committed in advance: if the request ends up
receiving less, there is no way to tell the application that more was
consumed than the CQE accounts for. Complete the request with what it has
got instead of retrying it. MSG_WAITALL is no longer honoured for
receives into incremental buffers or multi buffer bundles, they can
return a short count, with the request marked as failed like for other
short MSG_WAITALL transfers.

---

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