# CVE-2026-31425: rds: ib: reject FRMR registration before IB connection is established

> A null pointer dereference in the Linux kernel RDS InfiniBand driver allows local attackers to crash the system via a crafted sendmsg call.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Apr 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-31425, DEBIAN-CVE-2026-31425, GHSA-242h-4qqp-hpg2, ROOT-OS-DEBIAN-11-CVE-2026-31425, ROOT-OS-DEBIAN-12-CVE-2026-31425, ROOT-OS-DEBIAN-13-CVE-2026-31425, ROOT-OS-UBUNTU-2204-CVE-2026-31425, ROOT-OS-UBUNTU-2404-CVE-2026-31425, UBUNTU-CVE-2026-31425

## What is CVE-2026-31425?

CVE-2026-31425 is a medium-severity vulnerability in Linux kernel, published on 13 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

rds: ib: reject FRMR registration before IB connection is established

rds_ib_get_mr() extracts the rds_ib_connection from conn->c_transport_data
and passes it to rds_ib_reg_frmr() for FRWR memory registration. On a
fresh outgoing connection, ic is allocated in rds_ib_conn_alloc() with
i_cm_id = NULL because the connection worker has not yet called
rds_ib_conn_path_connect() to create the rdma_cm_id. When sendmsg() with
RDS_CMSG_RDMA_MAP is called on such a connection, the sendmsg path parses
the control message before any connection establishment, allowing
rds_ib_post_reg_frmr() to dereference ic->i_cm_id->qp and crash the
kernel.

The existing guard in rds_ib_reg_frmr() only checks for !ic (added in
commit 9e630bcb7701), which does not catch this case since ic is allocated
early and is always non-NULL once the connection object exists.

 KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
 RIP: 0010:rds_ib_post_reg_frmr+0x50e/0x920
 Call Trace:
  rds_ib_post_reg_frmr (net/rds/ib_frmr.c:167)
  rds_ib_map_frmr (net/rds/ib_frmr.c:252)
  rds_ib_reg_frmr (net/rds/ib_frmr.c:430)
  rds_ib_get_mr (net/rds/ib_rdma.c:615)
  __rds_rdma_map (net/rds/rdma.c:295)
  rds_cmsg_rdma_map (net/rds/rdma.c:860)
  rds_sendmsg (net/rds/send.c:1363)
  ____sys_sendmsg
  do_syscall_64

Add a check in rds_ib_get_mr() that verifies ic, i_cm_id, and qp are all
non-NULL before proceeding with FRMR registration, mirroring the guard
already present in rds_ib_post_inv(). Return -ENODEV when the connection
is not ready, which the existing error handling in rds_cmsg_send() converts
to -EAGAIN for userspace retry and triggers rds_conn_connect_if_down() to
start the connection worker.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-31425?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31425?

Apply the vendor's patch.

## Is CVE-2026-31425 being exploited?

There is no known exploitation of CVE-2026-31425 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31425 and fix it if it is affected.

What it is: CVE-2026-31425 is a medium-severity vulnerability in Linux kernel, published on 13 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-31425 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-31425/ (Markdown: https://insights.sbomify.com/CVE-2026-31425/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31425
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31425
- OSV: https://osv.dev/vulnerability/CVE-2026-31425

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31425/
Summaries are generated and may contain mistakes; the official description above is the record.