# CVE-2021-47076: RDMA/rxe: Return CQE error if invalid lkey was supplied

> A local attacker can trigger a kernel panic in the Linux kernel's RXE driver by sending an atomic operation with an invalid lkey, causing a denial of service.

- **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:** 1 Mar 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47076, GHSA-2gv4-5v5r-xjq2, ROOT-OS-DEBIAN-11-CVE-2021-47076, UBUNTU-CVE-2021-47076

## What is CVE-2021-47076?

CVE-2021-47076 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 Mar 2024. 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:

RDMA/rxe: Return CQE error if invalid lkey was supplied

RXE is missing update of WQE status in LOCAL_WRITE failures.  This caused
the following kernel panic if someone sent an atomic operation with an
explicitly wrong lkey.

[leonro@vm ~]$ mkt test
test_atomic_invalid_lkey (tests.test_atomic.AtomicTest) ...
 WARNING: CPU: 5 PID: 263 at drivers/infiniband/sw/rxe/rxe_comp.c:740 rxe_completer+0x1a6d/0x2e30 [rdma_rxe]
 Modules linked in: crc32_generic rdma_rxe ip6_udp_tunnel udp_tunnel rdma_ucm rdma_cm ib_umad ib_ipoib iw_cm ib_cm mlx5_ib ib_uverbs ib_core mlx5_core ptp pps_core
 CPU: 5 PID: 263 Comm: python3 Not tainted 5.13.0-rc1+ #2936
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 RIP: 0010:rxe_completer+0x1a6d/0x2e30 [rdma_rxe]
 Code: 03 0f 8e 65 0e 00 00 3b 93 10 06 00 00 0f 84 82 0a 00 00 4c 89 ff 4c 89 44 24 38 e8 2d 74 a9 e1 4c 8b 44 24 38 e9 1c f5 ff ff <0f> 0b e9 0c e8 ff ff b8 05 00 00 00 41 bf 05 00 00 00 e9 ab e7 ff
 RSP: 0018:ffff8880158af090 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: ffff888016a78000 RCX: ffffffffa0cf1652
 RDX: 1ffff9200004b442 RSI: 0000000000000004 RDI: ffffc9000025a210
 RBP: dffffc0000000000 R08: 00000000ffffffea R09: ffff88801617740b
 R10: ffffed1002c2ee81 R11: 0000000000000007 R12: ffff88800f3b63e8
 R13: ffff888016a78008 R14: ffffc9000025a180 R15: 000000000000000c
 FS:  00007f88b622a740(0000) GS:ffff88806d540000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f88b5a1fa10 CR3: 000000000d848004 CR4: 0000000000370ea0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  rxe_do_task+0x130/0x230 [rdma_rxe]
  rxe_rcv+0xb11/0x1df0 [rdma_rxe]
  rxe_loopback+0x157/0x1e0 [rdma_rxe]
  rxe_responder+0x5532/0x7620 [rdma_rxe]
  rxe_do_task+0x130/0x230 [rdma_rxe]
  rxe_rcv+0x9c8/0x1df0 [rdma_rxe]
  rxe_loopback+0x157/0x1e0 [rdma_rxe]
  rxe_requester+0x1efd/0x58c0 [rdma_rxe]
  rxe_do_task+0x130/0x230 [rdma_rxe]
  rxe_post_send+0x998/0x1860 [rdma_rxe]
  ib_uverbs_post_send+0xd5f/0x1220 [ib_uverbs]
  ib_uverbs_write+0x847/0xc80 [ib_uverbs]
  vfs_write+0x1c5/0x840
  ksys_write+0x176/0x1d0
  do_syscall_64+0x3f/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xae

## Which versions are affected by CVE-2021-47076?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47076?

Apply the vendor's patch.

## Is CVE-2021-47076 being exploited?

There is no known exploitation of CVE-2021-47076 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-2021-47076 and fix it if it is affected.

What it is: CVE-2021-47076 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 Mar 2024. 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-2021-47076 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-2021-47076/ (Markdown: https://insights.sbomify.com/CVE-2021-47076/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47076
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47076
- OSV: https://osv.dev/vulnerability/CVE-2021-47076

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47076/
Summaries are generated and may contain mistakes; the official description above is the record.