# CVE-2021-47080: RDMA/core: Prevent divide-by-zero error triggered by the user

> A local attacker can trigger a divide-by-zero error in the Linux kernel RDMA subsystem, causing a system crash.

- **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-2021-47080, GHSA-2h5w-7vpc-v582, UBUNTU-CVE-2021-47080

## What is CVE-2021-47080?

CVE-2021-47080 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/core: Prevent divide-by-zero error triggered by the user

The user_entry_size is supplied by the user and later used as a
denominator to calculate number of entries. The zero supplied by the user
will trigger the following divide-by-zero error:

 divide error: 0000 [#1] SMP KASAN PTI
 CPU: 4 PID: 497 Comm: c_repro Not tainted 5.13.0-rc1+ #281
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 RIP: 0010:ib_uverbs_handler_UVERBS_METHOD_QUERY_GID_TABLE+0x1b1/0x510
 Code: 87 59 03 00 00 e8 9f ab 1e ff 48 8d bd a8 00 00 00 e8 d3 70 41 ff 44 0f b7 b5 a8 00 00 00 e8 86 ab 1e ff 31 d2 4c 89 f0 31 ff <49> f7 f5 48 89 d6 48 89 54 24 10 48 89 04 24 e8 1b ad 1e ff 48 8b
 RSP: 0018:ffff88810416f828 EFLAGS: 00010246
 RAX: 0000000000000008 RBX: 1ffff1102082df09 RCX: ffffffff82183f3d
 RDX: 0000000000000000 RSI: ffff888105f2da00 RDI: 0000000000000000
 RBP: ffff88810416fa98 R08: 0000000000000001 R09: ffffed102082df5f
 R10: ffff88810416faf7 R11: ffffed102082df5e R12: 0000000000000000
 R13: 0000000000000000 R14: 0000000000000008 R15: ffff88810416faf0
 FS:  00007f5715efa740(0000) GS:ffff88811a700000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000020000840 CR3: 000000010c2e0001 CR4: 0000000000370ea0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  ? ib_uverbs_handler_UVERBS_METHOD_INFO_HANDLES+0x4b0/0x4b0
  ib_uverbs_cmd_verbs+0x1546/0x1940
  ib_uverbs_ioctl+0x186/0x240
  __x64_sys_ioctl+0x38a/0x1220
  do_syscall_64+0x3f/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xae

Weakness: CWE-369 (Divide By Zero)

## Which versions are affected by CVE-2021-47080?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47080?

Apply the vendor's patch.

## Is CVE-2021-47080 being exploited?

There is no known exploitation of CVE-2021-47080 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-2021-47080 and fix it if it is affected.

What it is: CVE-2021-47080 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-2021-47080 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-2021-47080/ (Markdown: https://insights.sbomify.com/CVE-2021-47080/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47080
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47080
- OSV: https://osv.dev/vulnerability/CVE-2021-47080

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47080/
Summaries are generated and may contain mistakes; the official description above is the record.