Linux: Out-of-bounds Read
CVE-2026-31774 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 90ced24c500ad4e129e9e34b7e56fd7849e350b6, c314b405dcc4d8b9041124f928f81715d6328bec, 1b655cd311344117d3052f6552cb20d9901c9d7c as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 90ced24c500ad4e129e9e34b7e56fd7849e350b6 or c314b405dcc4d8b9041124f928f81715d6328bec or 1b655cd311344117d3052f6552cb20d9901c9d7c or b948f9d5d3057b01188e36664e7c7604d1c8ecb5, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.81 or 6.18.22 or 6.19.12, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | a05d1f625c7aa681d8816bc0f10089289ad07aad up to, but not including, 90ced24c500ad4e129e9e34b7e56fd7849e350b6; a05d1f625c7aa681d8816bc0f10089289ad07aad up to, but not including, c314b405dcc4d8b9041124f928f81715d6328bec; a05d1f625c7aa681d8816bc0f10089289ad07aad up to, but not including, 1b655cd311344117d3052f6552cb20d9901c9d7c; a05d1f625c7aa681d8816bc0f10089289ad07aad up to, but not including, b948f9d5d3057b01188e36664e7c7604d1c8ecb5; 6.10 | 90ced24c500ad4e129e9e34b7e56fd7849e350b6, c314b405dcc4d8b9041124f928f81715d6328bec, 1b655cd311344117d3052f6552cb20d9901c9d7c, b948f9d5d3057b01188e36664e7c7604d1c8ecb5 |
| Linux | Linux Kernel | 6.10 up to, but not including, 6.12.81; 6.13 up to, but not including, 6.18.22; 6.19 up to, but not including, 6.19.12; 7.0 | 6.12.81, 6.18.22, 6.19.12 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H. Scored by CNA.
Official description
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: 1. io_recv(): sel.val = sr->len (ssize_t gets -1) 2. io_recv_buf_select(): arg.max_len = sel->val (size_t gets 0xFFFFFFFFFFFFFFFF) 3. io_ring_buffers_peek(): buf->len is not clamped because max_len is astronomically large 4. iov[].iov_len = 0xFFFFFFFF flows into io_bundle_nbufs() 5. 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Out-of-bounds Read vulnerabilities
- 8.1 High severity
- 8.8 High severity
- 7.1 High severity
- 7.3 High severity
- 7.1 High severity
- 7.1 High severity
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