CyberSecBulletin
CVE-2026-64440NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-64440 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists versions 37f642d47c3648a707df3ceb092eee1adffbfd28, 8c872b47c7fc32e95e0da1db7512388794adcd69, bb3b942da4123b55d1cacf19d1a7d5ba15dbf83a 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 0.27% 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 37f642d47c3648a707df3ceb092eee1adffbfd28 or 8c872b47c7fc32e95e0da1db7512388794adcd69 or bb3b942da4123b55d1cacf19d1a7d5ba15dbf83a or 918537a0fbed85aab61fa28ad75e6279070610c9, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.212 or 6.1.178 or 6.6.145 or 6.12.96, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux554c0a3abf216c991c5ebddcdb2c08689ecd290b up to, but not including, 37f642d47c3648a707df3ceb092eee1adffbfd28; 554c0a3abf216c991c5ebddcdb2c08689ecd290b up to, but not including, 8c872b47c7fc32e95e0da1db7512388794adcd69; 554c0a3abf216c991c5ebddcdb2c08689ecd290b up to, but not including, bb3b942da4123b55d1cacf19d1a7d5ba15dbf83a; 554c0a3abf216c991c5ebddcdb2c08689ecd290b up to, but not including, 918537a0fbed85aab61fa28ad75e6279070610c9; 554c0a3abf216c991c5ebddcdb2c08689ecd290b up to, but not including, 6f91621fc45025ad3c0be796b70e6e4cee22fc69; 554c0a3abf216c991c5ebddcdb2c08689ecd290b up to, but not including, 225b6d3fc7e99ac3d20b6c861d1e47d24e7ea31d; 554c0a3abf216c991c5ebddcdb2c08689ecd290b up to, but not including, f8001e1a516ba3b495728c65b61f799cbfad6bd0; 4.1237f642d47c3648a707df3ceb092eee1adffbfd28, 8c872b47c7fc32e95e0da1db7512388794adcd69, bb3b942da4123b55d1cacf19d1a7d5ba15dbf83a, 918537a0fbed85aab61fa28ad75e6279070610c9, 6f91621fc45025ad3c0be796b70e6e4cee22fc69, 225b6d3fc7e99ac3d20b6c861d1e47d24e7ea31d
LinuxLinux Kernel4.12 up to, but not including, 5.15.212; 5.16 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.4; 7.25.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39, 7.1.4

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
AdjacentThe attacker must be on the same local network segment.
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
NoneNo data is disclosed.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: staging: rtl8723bs: fix OOB write in HT_caps_handler() HT_caps_handler() iterates pIE->length bytes and writes into HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct HT_caps_element). Because pIE->length is a raw u8 from an over-the-air 802.11 AssocResponse frame and is never validated, a malicious AP can set it up to 255, causing up to 229 bytes of out-of-bounds writes into adjacent fields of struct mlme_ext_info. Truncate the iteration count to the size of HT_caps.u.HT_cap using umin() so that data from a longer-than-expected IE is silently ignored rather than written out of bounds, preserving interoperability with APs that pad the element. An early return on oversized IEs was considered but rejected: it would bypass the pmlmeinfo->HT_caps_enable = 1 assignment that precedes the loop, silently disabling HT mode for APs that append extra bytes to the HT Capabilities IE.

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: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

Spotted an error? Tell us.