CyberSecBulletin
CVE-2026-64324NVD status: Modified

Linux: Improper Validation of Array Index

Published Updated By the CyberSecBulletin desk

CVE-2026-64324 is a high-severity improper validation of array index 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 fdd6229d2ae9914c1f25d1041db0f4f312a4fa76, b54aee5652fcd7c23a0904a4623ec462c3edc70c, 12af328d2ee8d68e81ba612246d0b54b22d23e1f 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 0.16% 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 fdd6229d2ae9914c1f25d1041db0f4f312a4fa76 or b54aee5652fcd7c23a0904a4623ec462c3edc70c or 12af328d2ee8d68e81ba612246d0b54b22d23e1f or fb49099206c5c57af28a157249fa7bcb5518f99e, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 4.20 or 5.5 or 5.10.261 or 5.15.212, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux934f815345c09c290a9b9a9cfdddc203ec2117e8 up to, but not including, fdd6229d2ae9914c1f25d1041db0f4f312a4fa76; 22cc7323f090646c8cfb5939e6f15bdc2ed3fd27 up to, but not including, b54aee5652fcd7c23a0904a4623ec462c3edc70c; 7c4fa9ebfce69619d132fe703dc2e2cf62a13723 up to, but not including, 12af328d2ee8d68e81ba612246d0b54b22d23e1f; 5cc9745e2ea11aef7d5c9a42bc36f6cd3e1b4cc3 up to, but not including, fb49099206c5c57af28a157249fa7bcb5518f99e; 56e69e59751d20993f243fb7dd6991c4e522424c up to, but not including, 9442d75429b0c556292a7454fe888d54259f5240; 56e69e59751d20993f243fb7dd6991c4e522424c up to, but not including, 335202ab25b01fdd45889ff25eab70864686dea3; 56e69e59751d20993f243fb7dd6991c4e522424c up to, but not including, be87de7789a82a030a4896bc7683415ec9fa6f2b; 56e69e59751d20993f243fb7dd6991c4e522424c up to, but not including, 5f0419457f89dce1a3f1c8e62a3adf2f39ab8168; and 11 more rangesfdd6229d2ae9914c1f25d1041db0f4f312a4fa76, b54aee5652fcd7c23a0904a4623ec462c3edc70c, 12af328d2ee8d68e81ba612246d0b54b22d23e1f, fb49099206c5c57af28a157249fa7bcb5518f99e, 9442d75429b0c556292a7454fe888d54259f5240, 335202ab25b01fdd45889ff25eab70864686dea3
LinuxLinux Kernel4.19.320 up to, but not including, 4.20; 5.4.282 up to, but not including, 5.5; 5.10.224 up to, but not including, 5.10.261; 5.15.165 up to, but not including, 5.15.212; 6.1.105 up to, but not including, 6.1.178; 6.6.46 up to, but not including, 6.6.145; 6.10.5 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; and 1 more ranges4.20, 5.5, 5.10.261, 5.15.212, 6.1.178, 6.6.145

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: udf: validate free block extents against the partition length udf_free_blocks() checks the logical block number and count against the partition length, but drops the extent offset from that final bound. A crafted extent can pass the guard while logicalBlockNum + offset + count points past the partition, which later indexes past the space bitmap array. A single ftruncate(2) on a file backed by such an extent reliably panics the kernel. This is a local availability issue. On desktop systems where UDisks/polkit allows the active user to mount removable UDF media without CAP_SYS_ADMIN, an unprivileged local user can supply the crafted filesystem and trigger the panic by truncating a writable file on it. Systems that require root or CAP_SYS_ADMIN to mount the image have a higher prerequisite. No confidentiality or integrity impact is claimed: the reproduced primitive is an out-of-bounds read of a bitmap pointer slot followed by a kernel panic. Use the already computed logicalBlockNum + offset + count value for the partition length check. Also make load_block_bitmap() reject an out-of-range block group before indexing s_block_bitmap[], so corrupted callers cannot walk past the flexible array.

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

The underlying weakness: Improper Validation of Array Index

The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.

How developers prevent this class of flaw

  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, Ada allows the programmer to constrain the values of a variable and languages such as Java and Ruby will allow the programmer to handle exceptions when an out-of-bounds index is accessed.
  • Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment. For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND.

More Improper Validation of Array Index vulnerabilities (CWE-129)

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 Improper Validation of Array Index vulnerabilities

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