CyberSecBulletin
CVE-2026-64323NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-64323 is a high-severity out-of-bounds write 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 0ad2d09a8d66fa8dc6f9b70d660b5fb4478ea934, 883962731420ec271ed8c1cd76524f4b17faa982, 2900e02a0dd4fc30ac9840e7ce4ca0b041ab0d63 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 0.17% 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 0ad2d09a8d66fa8dc6f9b70d660b5fb4478ea934 or 883962731420ec271ed8c1cd76524f4b17faa982 or 2900e02a0dd4fc30ac9840e7ce4ca0b041ab0d63 or bb0d384c1f42a5b7ace0bd88fee80b9bb1d49acb, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.261 or 5.15.212 or 6.1.178 or 6.6.145, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxfa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, 0ad2d09a8d66fa8dc6f9b70d660b5fb4478ea934; fa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, 883962731420ec271ed8c1cd76524f4b17faa982; fa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, 2900e02a0dd4fc30ac9840e7ce4ca0b041ab0d63; fa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, bb0d384c1f42a5b7ace0bd88fee80b9bb1d49acb; fa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, 55287a3555ff0515b3aff181d2c08c0462a41709; fa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, e610fb113cdfa8bf4247c9bf4f2337b81ad4ddad; fa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, 74580fdf022909e184223cacc364feb826982d96; fa5e08156335d0687c85b4e724db9448fb166601 up to, but not including, d8202786b3d75125c84ebc4de6d946f92fde0ee8; and 1 more ranges0ad2d09a8d66fa8dc6f9b70d660b5fb4478ea934, 883962731420ec271ed8c1cd76524f4b17faa982, 2900e02a0dd4fc30ac9840e7ce4ca0b041ab0d63, bb0d384c1f42a5b7ace0bd88fee80b9bb1d49acb, 55287a3555ff0515b3aff181d2c08c0462a41709, e610fb113cdfa8bf4247c9bf4f2337b81ad4ddad
LinuxLinux Kernel2.6.26 up to, but not including, 5.10.261; 5.11 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, 7.1.45.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39

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: udf: validate VAT header length against the VAT inode size udf_load_vat() takes the virtual partition's start offset straight from the on-disk VAT 2.0 header without checking it against the VAT inode size: map->s_type_specific.s_virtual.s_start_offset = le16_to_cpu(vat20->lengthHeader); map->s_type_specific.s_virtual.s_num_entries = (sbi->s_vat_inode->i_size - map->s_type_specific.s_virtual.s_start_offset) >> 2; lengthHeader is a fully attacker-controlled 16-bit value. If it exceeds the VAT inode size, the s_num_entries subtraction underflows to a huge count, which defeats the "block > s_num_entries" bound in udf_get_pblock_virt15(); and on the ICB-inline path that function reads ((__le32 *)(iinfo->i_data + s_start_offset))[block] so a large s_start_offset indexes past the inode's in-ICB data. Mounting a crafted UDF image with a virtual (VAT) partition then triggers an out-of-bounds read. Reject a VAT whose header length does not leave room for at least one entry within the VAT inode.

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

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