CVE-2026-31449
Out-of-Bounds Read in Linux Kernel ext4 Extent Index Validation
Publication date: 2026-04-22
Last updated on: 2026-04-27
Assigner: kernel.org
Description
Description
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | * |
| linux | kernel | * |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
Attack-Flow Graph
AI Powered Q&A
What immediate steps should I take to mitigate this vulnerability?
The vulnerability in the Linux kernel ext4 subsystem involves improper validation of index bounds in ext4_ext_correct_indexes, which can cause slab-out-of-bounds reads.
To mitigate this vulnerability, you should update your Linux kernel to a version where this issue has been fixed. The fix involves validating the index pointer against EXT_LAST_INDEX() to prevent out-of-range access.
Applying the latest kernel patches or upgrading to a kernel version released after 2026-04-22, when this vulnerability was fixed, is the recommended immediate step.
Can you explain this vulnerability to me?
This vulnerability exists in the Linux kernel's ext4 filesystem code, specifically in the function ext4_ext_correct_indexes. The function walks up the extent tree to correct index entries when the first extent in a leaf is modified. However, before accessing a particular index pointer (p_idx), the code does not validate whether p_idx is within the valid range of index entries for that level.
If the on-disk extent header contains a corrupted or maliciously crafted value for eh_entries, p_idx can point beyond the allocated buffer. This leads to a slab-out-of-bounds read, which is a type of memory access error.
The fix involves validating the p_idx pointer against the maximum allowed index (EXT_LAST_INDEX()) before accessing it, returning an error (-EFSCORRUPTED) if the pointer is out of range, consistent with other bounds checks in the ext4 extent tree code.
How can this vulnerability impact me? :
This vulnerability can cause the Linux kernel to perform an out-of-bounds read in memory when processing corrupted or crafted ext4 filesystem metadata. Such out-of-bounds reads can lead to system instability, crashes, or potentially expose sensitive kernel memory contents.
While the description does not explicitly mention privilege escalation or code execution, out-of-bounds reads can be leveraged by attackers to gain information about kernel memory layout or cause denial of service conditions.