CyberSecBulletin
CVE-2026-64026NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-64026 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.8 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 a05bf6d9e621fa71e89ccebe3047ba45218d7b38, b94a6ccbaf1104dd980150a65fdeb2f69d17d2f5, 46cb765e2e5ad52303ea157e10d370bb6b7acbbf 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 0.11% 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 a05bf6d9e621fa71e89ccebe3047ba45218d7b38 or b94a6ccbaf1104dd980150a65fdeb2f69d17d2f5 or 46cb765e2e5ad52303ea157e10d370bb6b7acbbf or c580087743712112778a06d65a4074053072d7bf, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.143 or 6.12.93 or 6.18.35 or 7.0.11, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxd0d5c0cd1e711c98703f3544c1e6fc1372898de5 up to, but not including, a05bf6d9e621fa71e89ccebe3047ba45218d7b38; d0d5c0cd1e711c98703f3544c1e6fc1372898de5 up to, but not including, b94a6ccbaf1104dd980150a65fdeb2f69d17d2f5; d0d5c0cd1e711c98703f3544c1e6fc1372898de5 up to, but not including, 46cb765e2e5ad52303ea157e10d370bb6b7acbbf; d0d5c0cd1e711c98703f3544c1e6fc1372898de5 up to, but not including, c580087743712112778a06d65a4074053072d7bf; d0d5c0cd1e711c98703f3544c1e6fc1372898de5 up to, but not including, d2bc90cf6c75cb96d2ce549be6c35efa3099d25b; 5.3a05bf6d9e621fa71e89ccebe3047ba45218d7b38, b94a6ccbaf1104dd980150a65fdeb2f69d17d2f5, 46cb765e2e5ad52303ea157e10d370bb6b7acbbf, c580087743712112778a06d65a4074053072d7bf, d2bc90cf6c75cb96d2ce549be6c35efa3099d25b
LinuxLinux Kernel5.3.1 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.11; 5.3; 7.16.6.143, 6.12.93, 6.18.35, 7.0.11

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
HighData or code can be modified at will.
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:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix DATA decrypt vs splice() by copying data to buffer in recvmsg This improves the fix for CVE-2026-43500. Fix the pagecache corruption from in-place decryption of a DATA packet transmitted locally by splice() by getting rid of the packet sharing in the I/O thread and unconditionally extracting the packet content into a bounce buffer in which the buffer is decrypted. recvmsg() (or the kernel equivalent) then copies the data from the bounce buffer to the destination buffer. The sk_buff then remains unmodified. This has an additional advantage in that the packet is then arranged in the buffer with the correct alignment required for the crypto algorithms to process directly. The performance of the crypto does seem to be a little faster and, surprisingly, the unencrypted performance doesn't seem to change much - possibly due to removing complexity from the I/O thread. Yet another advantage is that the I/O thread doesn't have to copy packets which would slow down packet distribution, ACK generation, etc.. The buffer belongs to the call and is allocated initially at 2K, sufficiently large to hold a whole jumbo subpacket, but the buffer will be increased in size if needed. However, to take this work, MSG_PEEK may cause a later packet to be decrypted into the buffer, in which case the earlier one will need re-decrypting for a subsequent recvmsg(). Note that rx_pkt_offset may legitimately see 0 as a valid offset now, so switch to using USHRT_MAX to indicate an invalid offset. Note also that I would generally prefer to replace the buffers of the current sk_buff with a new kmalloc'd buffer of the right size, ditching the old data and frags as this makes the handling of MSG_PEEK easier and removes the re-decryption issue, but this looks like quite a complicated thing to achieve. skb_morph() looks half way to what I want, but I don't want to have to allocate a new sk_buff.

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. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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