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CVE-2026-46123NVD status: Undergoing Analysis

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-46123 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.7 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists versions 4236e55b2d9d1ffd3b4bdf8ebbb86e5a0a526b4a, fd91fa2678ab603dfb285416c1cf3843d7be1e41, ed41c81d30b211a671667259c3b5feeba0e062d5 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 0.14% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 4236e55b2d9d1ffd3b4bdf8ebbb86e5a0a526b4a or fd91fa2678ab603dfb285416c1cf3843d7be1e41 or ed41c81d30b211a671667259c3b5feeba0e062d5 or 6c1730099a6fc18b183bd6c1adad3b54adcaeda9, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.209 or 6.1 or 6.1.175 or 6.6.140, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxcf2719a21fdb9d4c8e9c834d279163609bef575d up to, but not including, 4236e55b2d9d1ffd3b4bdf8ebbb86e5a0a526b4a; 160fbcf3bfb93c3c086427f9f4c8bc70f217e9be up to, but not including, fd91fa2678ab603dfb285416c1cf3843d7be1e41; 160fbcf3bfb93c3c086427f9f4c8bc70f217e9be up to, but not including, ed41c81d30b211a671667259c3b5feeba0e062d5; 160fbcf3bfb93c3c086427f9f4c8bc70f217e9be up to, but not including, 6c1730099a6fc18b183bd6c1adad3b54adcaeda9; 160fbcf3bfb93c3c086427f9f4c8bc70f217e9be up to, but not including, b40cdd1b1370d76e9e760af4490cb4a351cceead; 160fbcf3bfb93c3c086427f9f4c8bc70f217e9be up to, but not including, e6b4296f170d949ebba937cf6a3f247ec9550d2c; 160fbcf3bfb93c3c086427f9f4c8bc70f217e9be up to, but not including, 21bd244b6de5d2fe1063c23acc93fbdd2b20d112; 9b67438e315b925a699f0178f4a48baf3d2d6ef4; and 3 more ranges4236e55b2d9d1ffd3b4bdf8ebbb86e5a0a526b4a, fd91fa2678ab603dfb285416c1cf3843d7be1e41, ed41c81d30b211a671667259c3b5feeba0e062d5, 6c1730099a6fc18b183bd6c1adad3b54adcaeda9, b40cdd1b1370d76e9e760af4490cb4a351cceead, e6b4296f170d949ebba937cf6a3f247ec9550d2c
LinuxLinux Kernel5.15.78 up to, but not including, 5.15.209; 6.0.8 up to, but not including, 6.1; 6.1.1 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.140; 6.7 up to, but not including, 6.12.88; 6.13 up to, but not including, 6.18.30; 6.19 up to, but not including, 7.0.7; 6.1; and 1 more ranges5.15.209, 6.1, 6.1.175, 6.6.140, 6.12.88, 6.18.30

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
NoneNo account or login is needed.
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:N/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: Bluetooth: virtio_bt: clamp rx length before skb_put virtbt_rx_work() calls skb_put(skb, len) where len comes directly from virtqueue_get_buf() with no validation against the buffer we posted to the device. The RX skb is allocated in virtbt_add_inbuf() and exposed to virtio as exactly 1000 bytes via sg_init_one(). Checking len against skb_tailroom(skb) is not sufficient because alloc_skb() can leave more tailroom than the 1000 bytes actually handed to the device. A malicious or buggy backend can therefore report used.len between 1001 and skb_tailroom(skb), causing skb_put() to include uninitialized kernel heap bytes that were never written by the device. The same path also accepts len == 0, in which case skb_put(skb, 0) leaves the skb empty but virtbt_rx_handle() still reads the pkt_type byte from skb->data, consuming uninitialized memory. Define VIRTBT_RX_BUF_SIZE once and reuse it in alloc_skb() and sg_init_one(), and gate virtbt_rx_work() on that same constant so the bound checked matches the buffer actually exposed to the device. Reject used.len == 0 in the same gate so an empty completion can no longer reach virtbt_rx_handle(). Use bt_dev_err_ratelimited() because the length value comes from an untrusted backend that can otherwise flood the kernel log. Same class of bug as commit c04db81cd028 ("net/9p: Fix buffer overflow in USB transport layer"), which hardened the USB 9p transport against unchecked device-reported length.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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