# CVE-2026-46133: RDMA/rxe: Reject unknown opcodes before ICRC processing

> A remote attacker can cause a kernel panic via a crafted UDP packet in the Linux RDMA Soft RoCE driver, requiring the module to be loaded.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-89102, BELL-CVE-2026-46133, DEBIAN-CVE-2026-46133, GHSA-gvjm-hrcm-hvm6, ROOT-OS-DEBIAN-11-CVE-2026-46133, ROOT-OS-DEBIAN-12-CVE-2026-46133, ROOT-OS-UBUNTU-2204-CVE-2026-46133, ROOT-OS-UBUNTU-2404-CVE-2026-46133, UBUNTU-CVE-2026-46133

## What is CVE-2026-46133?

CVE-2026-46133 is a high-severity memory corruption vulnerability in Linux kernel, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

RDMA/rxe: Reject unknown opcodes before ICRC processing

Even after applying commit 7244491dab34 ("RDMA/rxe: Validate pad and ICRC
before payload_size() in rxe_rcv"), a single unauthenticated UDP packet
can still trigger panic.  That patch handled payload_size() underflow only
for valid opcodes with short packets, not for packets carrying an unknown
opcode.  The unknown-opcode OOB read described below predates that commit
and reaches back to the initial Soft RoCE driver.

The check added there reads

    pkt->paylen < header_size(pkt) + bth_pad(pkt) + RXE_ICRC_SIZE

where header_size(pkt) expands to rxe_opcode[pkt->opcode].length.  The
rxe_opcode[] array has 256 entries but is only populated for defined IB
opcodes; any other entry (for example opcode 0xff) is zero-initialized, so
length == 0 and the check degenerates to

    pkt->paylen < 0 + bth_pad(pkt) + RXE_ICRC_SIZE

which does not constrain pkt->paylen enough.  rxe_icrc_hdr() then computes

    rxe_opcode[pkt->opcode].length - RXE_BTH_BYTES

which underflows when length == 0 and passes a huge value to rxe_crc32(),
causing an out-of-bounds read of the skb payload.

Reproduced on v7.0-rc7 with that fix applied, QEMU/KVM with
CONFIG_RDMA_RXE=y and CONFIG_KASAN=y, after

    rdma link add rxe0 type rxe netdev eth0

A single 48-byte UDP packet to port 4791 with BTH opcode=0xff and
QPN=IB_MULTICAST_QPN triggers:

    BUG: KASAN: slab-out-of-bounds in crc32_le+0x115/0x170
    Read of size 1 at addr ...
    The buggy address is located 0 bytes to the right of
     allocated 704-byte region
    Call Trace:
     crc32_le+0x115/0x170
     rxe_icrc_hdr.isra.0+0x226/0x300
     rxe_icrc_check+0x13f/0x3a0
     rxe_rcv+0x6e1/0x16e0
     rxe_udp_encap_recv+0x20a/0x320
     udp_queue_rcv_one_skb+0x7ed/0x12c0

Subsequent packets with the same shape fault on unmapped memory and panic
the kernel.  The trigger requires only module load and "rdma link add"; no
QP, no connection, and no authentication.

Fix this by rejecting packets whose opcode has no rxe_opcode[] entry,
detected via the zero mask or zero length, before any length arithmetic
runs.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-46133?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46133?

Apply the vendor's patch.

## Is CVE-2026-46133 being exploited?

There is no known exploitation of CVE-2026-46133 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-2026-46133 and fix it if it is affected.

What it is: CVE-2026-46133 is a high-severity memory corruption vulnerability in Linux kernel, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-46133 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-2026-46133/ (Markdown: https://insights.sbomify.com/CVE-2026-46133/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46133
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46133
- OSV: https://osv.dev/vulnerability/CVE-2026-46133

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46133/
Summaries are generated and may contain mistakes; the official description above is the record.