# CVE-2021-47246: net/mlx5e: Fix page reclaim for dead peer hairpin

> A memory leak in the Linux kernel mlx5 driver causes a denial of service when a peer network device is removed before hairpin flow deletion.

- **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:** 21 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47246, GHSA-c655-qwvw-wfqm, UBUNTU-CVE-2021-47246

## What is CVE-2021-47246?

CVE-2021-47246 is a medium-severity memory corruption vulnerability in Linux kernel, published on 21 May 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:

net/mlx5e: Fix page reclaim for dead peer hairpin

When adding a hairpin flow, a firmware-side send queue is created for
the peer net device, which claims some host memory pages for its
internal ring buffer. If the peer net device is removed/unbound before
the hairpin flow is deleted, then the send queue is not destroyed which
leads to a stack trace on pci device remove:

[ 748.005230] mlx5_core 0000:08:00.2: wait_func:1094:(pid 12985): MANAGE_PAGES(0x108) timeout. Will cause a leak of a command resource
[ 748.005231] mlx5_core 0000:08:00.2: reclaim_pages:514:(pid 12985): failed reclaiming pages: err -110
[ 748.001835] mlx5_core 0000:08:00.2: mlx5_reclaim_root_pages:653:(pid 12985): failed reclaiming pages (-110) for func id 0x0
[ 748.002171] ------------[ cut here ]------------
[ 748.001177] FW pages counter is 4 after reclaiming all pages
[ 748.001186] WARNING: CPU: 1 PID: 12985 at drivers/net/ethernet/mellanox/mlx5/core/pagealloc.c:685 mlx5_reclaim_startup_pages+0x34b/0x460 [mlx5_core]                      [  +0.002771] Modules linked in: cls_flower mlx5_ib mlx5_core ptp pps_core act_mirred sch_ingress openvswitch nsh xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 br_netfilter rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi rdma_cm ib_umad ib_ipoib iw_cm ib_cm ib_uverbs ib_core overlay fuse [last unloaded: pps_core]
[ 748.007225] CPU: 1 PID: 12985 Comm: tee Not tainted 5.12.0+ #1
[ 748.001376] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[ 748.002315] RIP: 0010:mlx5_reclaim_startup_pages+0x34b/0x460 [mlx5_core]
[ 748.001679] Code: 28 00 00 00 0f 85 22 01 00 00 48 81 c4 b0 00 00 00 31 c0 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 c7 c7 40 cc 19 a1 e8 9f 71 0e e2 <0f> 0b e9 30 ff ff ff 48 c7 c7 a0 cc 19 a1 e8 8c 71 0e e2 0f 0b e9
[ 748.003781] RSP: 0018:ffff88815220faf8 EFLAGS: 00010286
[ 748.001149] RAX: 0000000000000000 RBX: ffff8881b4900280 RCX: 0000000000000000
[ 748.001445] RDX: 0000000000000027 RSI: 0000000000000004 RDI: ffffed102a441f51
[ 748.001614] RBP: 00000000000032b9 R08: 0000000000000001 R09: ffffed1054a15ee8
[ 748.001446] R10: ffff8882a50af73b R11: ffffed1054a15ee7 R12: fffffbfff07c1e30
[ 748.001447] R13: dffffc0000000000 R14: ffff8881b492cba8 R15: 0000000000000000
[ 748.001429] FS:  00007f58bd08b580(0000) GS:ffff8882a5080000(0000) knlGS:0000000000000000
[ 748.001695] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 748.001309] CR2: 000055a026351740 CR3: 00000001d3b48006 CR4: 0000000000370ea0
[ 748.001506] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 748.001483] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 748.001654] Call Trace:
[ 748.000576]  ? mlx5_satisfy_startup_pages+0x290/0x290 [mlx5_core]
[ 748.001416]  ? mlx5_cmd_teardown_hca+0xa2/0xd0 [mlx5_core]
[ 748.001354]  ? mlx5_cmd_init_hca+0x280/0x280 [mlx5_core]
[ 748.001203]  mlx5_function_teardown+0x30/0x60 [mlx5_core]
[ 748.001275]  mlx5_uninit_one+0xa7/0xc0 [mlx5_core]
[ 748.001200]  remove_one+0x5f/0xc0 [mlx5_core]
[ 748.001075]  pci_device_remove+0x9f/0x1d0
[ 748.000833]  device_release_driver_internal+0x1e0/0x490
[ 748.001207]  unbind_store+0x19f/0x200
[ 748.000942]  ? sysfs_file_ops+0x170/0x170
[ 748.001000]  kernfs_fop_write_iter+0x2bc/0x450
[ 748.000970]  new_sync_write+0x373/0x610
[ 748.001124]  ? new_sync_read+0x600/0x600
[ 748.001057]  ? lock_acquire+0x4d6/0x700
[ 748.000908]  ? lockdep_hardirqs_on_prepare+0x400/0x400
[ 748.001126]  ? fd_install+0x1c9/0x4d0
[ 748.000951]  vfs_write+0x4d0/0x800
[ 748.000804]  ksys_write+0xf9/0x1d0
[ 748.000868]  ? __x64_sys_read+0xb0/0xb0
[ 748.000811]  ? filp_open+0x50/0x50
[ 748.000919]  ? syscall_enter_from_user_mode+0x1d/0x50
[ 748.001223]  do_syscall_64+0x3f/0x80
[ 748.000892]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 748.00
---truncated---

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2021-47246?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47246?

Apply the vendor's patch.

## Is CVE-2021-47246 being exploited?

There is no known exploitation of CVE-2021-47246 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-2021-47246 and fix it if it is affected.

What it is: CVE-2021-47246 is a medium-severity memory corruption vulnerability in Linux kernel, published on 21 May 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-2021-47246 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-2021-47246/ (Markdown: https://insights.sbomify.com/CVE-2021-47246/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47246
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47246
- OSV: https://osv.dev/vulnerability/CVE-2021-47246

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47246/
Summaries are generated and may contain mistakes; the official description above is the record.