CVE-2026-31774High· 7.1▾ Twilight

io_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs()

In the Linux kernel, the following vulnerability has been resolved: io_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs() sqe->len is __u32 but gets stored into sr->len which is int. When userspace passes sqe->len values excee…

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score39/ 100 · Low

impact 39.1 · likelihood 0 · exploitation 0

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Proof of concept

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Published

May 1, 2026

Updated

Oct 19, 2026

CVSS

7.1

Vendor

Linux

Product

Linux

CWE

—

Depth score

39 · Low

EPSS

0.13% · p2

Platforms

—

Source

CVEORG

Vector

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

CISA SSVC

decided 2026-10-16

Exploitation: none
Automatable: no
Technical impact: partial

Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.

EPSS history

Exploit-prediction probability, daily snapshots since Oct 16.

0.2% → 0.1%

Timeline

Disclosure to exploitation, from the record and what we observed since indexing it.

3 events · 171 days

May 1, 2026Published
Disclosed via CVEORG
Oct 16, 2026EPSS first tracked
0.2%
Oct 19, 2026Record revised
Last analysed / modified upstream

Linux #cve.org

Affected

Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < 90ced24c500ad4e129e9e34b7e56fd7849e350b6
Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < c314b405dcc4d8b9041124f928f81715d6328bec
Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < 1b655cd311344117d3052f6552cb20d9901c9d7c
Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < b948f9d5d3057b01188e36664e7c7604d1c8ecb5
Linux 6.10

Full technical detail▾

Overview

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

io_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs()

sqe->len is __u32 but gets stored into sr->len which is int. When userspace passes sqe->len values exceeding INT_MAX (e.g. 0xFFFFFFFF), sr->len overflows to a negative value. This negative value propagates through the bundle recv/send path:

io_recv(): sel.val = sr->len (ssize_t gets -1)
io_recv_buf_select(): arg.max_len = sel->val (size_t gets 0xFFFFFFFFFFFFFFFF)
io_ring_buffers_peek(): buf->len is not clamped because max_len is astronomically large
iov[].iov_len = 0xFFFFFFFF flows into io_bundle_nbufs()
io_bundle_nbufs(): min_t(int, 0xFFFFFFFF, ret) yields -1, causing ret to increase instead of decrease, creating an infinite loop that reads past the allocated iov[] array

This results in a slab-out-of-bounds read in io_bundle_nbufs() from the kmalloc-64 slab, as nbufs increments past the allocated iovec entries.

BUG: KASAN: slab-out-of-bounds in io_bundle_nbufs+0x128/0x160 Read of size 8 at addr ffff888100ae05c8 by task exp/145 Call Trace: io_bundle_nbufs+0x128/0x160 io_recv_finish+0x117/0xe20 io_recv+0x2db/0x1160

Fix this by rejecting negative sr->len values early in both io_sendmsg_prep() and io_recvmsg_prep(). Since sqe->len is __u32, any value > INT_MAX indicates overflow and is not a valid length.

Affected

Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < 90ced24c500ad4e129e9e34b7e56fd7849e350b6
Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < c314b405dcc4d8b9041124f928f81715d6328bec
Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < 1b655cd311344117d3052f6552cb20d9901c9d7c
Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < b948f9d5d3057b01188e36664e7c7604d1c8ecb5
Linux 6.10

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

References

Related vulnerabilities

Connected by shared product, vendor, weakness, or advisory.

#cve.org

io_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs()

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score39/ 100 · Low

impact 39.1 · likelihood 0 · exploitation 0

Overview

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

io_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs()

io_recv(): sel.val = sr->len (ssize_t gets -1)

io_recv_buf_select(): arg.max_len = sel->val (size_t gets 0xFFFFFFFFFFFFFFFF)

io_ring_buffers_peek(): buf->len is not clamped because max_len is astronomically large

iov[].iov_len = 0xFFFFFFFF flows into io_bundle_nbufs()

io_bundle_nbufs(): min_t(int, 0xFFFFFFFF, ret) yields -1, causing ret to increase instead of decrease, creating an infinite loop that reads past the allocated iov[] array

This results in a slab-out-of-bounds read in io_bundle_nbufs() from the kmalloc-64 slab, as nbufs increments past the allocated iovec entries.

Fix this by rejecting negative sr->len values early in both io_sendmsg_prep() and io_recvmsg_prep(). Since sqe->len is __u32, any value > INT_MAX indicates overflow and is not a valid length.

Affected

Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < 90ced24c500ad4e129e9e34b7e56fd7849e350b6

Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < c314b405dcc4d8b9041124f928f81715d6328bec

Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < 1b655cd311344117d3052f6552cb20d9901c9d7c

Linux >= a05d1f625c7aa681d8816bc0f10089289ad07aad < b948f9d5d3057b01188e36664e7c7604d1c8ecb5

Linux 6.10