# CVE-2021-47078: RDMA/rxe: Clear all QP fields if creation failed

> A use-after-free vulnerability in the Linux kernel RDMA/rxe driver allows attackers to cause a denial of service or potentially execute code.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2021-47078, GHSA-c56c-8vvg-gr68, UBUNTU-CVE-2021-47078

## What is CVE-2021-47078?

CVE-2021-47078 is a high-severity use after free 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: Clear all QP fields if creation failed

rxe_qp_do_cleanup() relies on valid pointer values in QP for the properly
created ones, but in case rxe_qp_from_init() failed it was filled with
garbage and caused tot the following error.

  refcount_t: underflow; use-after-free.
  WARNING: CPU: 1 PID: 12560 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
  Modules linked in:
  CPU: 1 PID: 12560 Comm: syz-executor.4 Not tainted 5.12.0-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
  Code: e9 db fe ff ff 48 89 df e8 2c c2 ea fd e9 8a fe ff ff e8 72 6a a7 fd 48 c7 c7 e0 b2 c1 89 c6 05 dc 3a e6 09 01 e8 ee 74 fb 04 <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55
  RSP: 0018:ffffc900097ceba8 EFLAGS: 00010286
  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
  RDX: 0000000000040000 RSI: ffffffff815bb075 RDI: fffff520012f9d67
  RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
  R10: ffffffff815b4eae R11: 0000000000000000 R12: ffff8880322a4800
  R13: ffff8880322a4940 R14: ffff888033044e00 R15: 0000000000000000
  FS:  00007f6eb2be3700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007fdbe5d41000 CR3: 000000001d181000 CR4: 00000000001506e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   __refcount_sub_and_test include/linux/refcount.h:283 [inline]
   __refcount_dec_and_test include/linux/refcount.h:315 [inline]
   refcount_dec_and_test include/linux/refcount.h:333 [inline]
   kref_put include/linux/kref.h:64 [inline]
   rxe_qp_do_cleanup+0x96f/0xaf0 drivers/infiniband/sw/rxe/rxe_qp.c:805
   execute_in_process_context+0x37/0x150 kernel/workqueue.c:3327
   rxe_elem_release+0x9f/0x180 drivers/infiniband/sw/rxe/rxe_pool.c:391
   kref_put include/linux/kref.h:65 [inline]
   rxe_create_qp+0x2cd/0x310 drivers/infiniband/sw/rxe/rxe_verbs.c:425
   _ib_create_qp drivers/infiniband/core/core_priv.h:331 [inline]
   ib_create_named_qp+0x2ad/0x1370 drivers/infiniband/core/verbs.c:1231
   ib_create_qp include/rdma/ib_verbs.h:3644 [inline]
   create_mad_qp+0x177/0x2d0 drivers/infiniband/core/mad.c:2920
   ib_mad_port_open drivers/infiniband/core/mad.c:3001 [inline]
   ib_mad_init_device+0xd6f/0x1400 drivers/infiniband/core/mad.c:3092
   add_client_context+0x405/0x5e0 drivers/infiniband/core/device.c:717
   enable_device_and_get+0x1cd/0x3b0 drivers/infiniband/core/device.c:1331
   ib_register_device drivers/infiniband/core/device.c:1413 [inline]
   ib_register_device+0x7c7/0xa50 drivers/infiniband/core/device.c:1365
   rxe_register_device+0x3d5/0x4a0 drivers/infiniband/sw/rxe/rxe_verbs.c:1147
   rxe_add+0x12fe/0x16d0 drivers/infiniband/sw/rxe/rxe.c:247
   rxe_net_add+0x8c/0xe0 drivers/infiniband/sw/rxe/rxe_net.c:503
   rxe_newlink drivers/infiniband/sw/rxe/rxe.c:269 [inline]
   rxe_newlink+0xb7/0xe0 drivers/infiniband/sw/rxe/rxe.c:250
   nldev_newlink+0x30e/0x550 drivers/infiniband/core/nldev.c:1555
   rdma_nl_rcv_msg+0x36d/0x690 drivers/infiniband/core/netlink.c:195
   rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline]
   rdma_nl_rcv+0x2ee/0x430 drivers/infiniband/core/netlink.c:259
   netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
   netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338
   netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927
   sock_sendmsg_nosec net/socket.c:654 [inline]
   sock_sendmsg+0xcf/0x120 net/socket.c:674
   ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
   ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
   __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
   do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
   entry_SYSCALL_64_after_hwframe+0
---truncated---

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-47078?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47078?

Apply the vendor's patch.

## Is CVE-2021-47078 being exploited?

There is no known exploitation of CVE-2021-47078 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-2021-47078 and fix it if it is affected.

What it is: CVE-2021-47078 is a high-severity use after free 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-2021-47078 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-2021-47078/ (Markdown: https://insights.sbomify.com/CVE-2021-47078/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47078
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47078
- OSV: https://osv.dev/vulnerability/CVE-2021-47078

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47078/
Summaries are generated and may contain mistakes; the official description above is the record.