# CVE-2021-47400: net: hns3: do not allow call hns3_nic_net_open repeatedly > A race condition in the HNS3 network driver allows repeated calls to net_open, causing a kernel bug and denial of service. - **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:** 21 May 2024 - **Updated:** 5 Aug 2026 - **Also known as:** DEBIAN-CVE-2021-47400, GHSA-wr76-p7r7-8vjv, UBUNTU-CVE-2021-47400 ## What is CVE-2021-47400? CVE-2021-47400 is a high-severity 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: hns3: do not allow call hns3_nic_net_open repeatedly hns3_nic_net_open() is not allowed to called repeatly, but there is no checking for this. When doing device reset and setup tc concurrently, there is a small oppotunity to call hns3_nic_net_open repeatedly, and cause kernel bug by calling napi_enable twice. The calltrace information is like below: [ 3078.222780] ------------[ cut here ]------------ [ 3078.230255] kernel BUG at net/core/dev.c:6991! [ 3078.236224] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP [ 3078.243431] Modules linked in: hns3 hclgevf hclge hnae3 vfio_iommu_type1 vfio_pci vfio_virqfd vfio pv680_mii(O) [ 3078.258880] CPU: 0 PID: 295 Comm: kworker/u8:5 Tainted: G O 5.14.0-rc4+ #1 [ 3078.269102] Hardware name: , BIOS KpxxxFPGA 1P B600 V181 08/12/2021 [ 3078.276801] Workqueue: hclge hclge_service_task [hclge] [ 3078.288774] pstate: 60400009 (nZCv daif +PAN -UAO -TCO BTYPE=--) [ 3078.296168] pc : napi_enable+0x80/0x84 tc qdisc sho[w 3d0e7v8 .e3t0h218 79] lr : hns3_nic_net_open+0x138/0x510 [hns3] [ 3078.314771] sp : ffff8000108abb20 [ 3078.319099] x29: ffff8000108abb20 x28: 0000000000000000 x27: ffff0820a8490300 [ 3078.329121] x26: 0000000000000001 x25: ffff08209cfc6200 x24: 0000000000000000 [ 3078.339044] x23: ffff0820a8490300 x22: ffff08209cd76000 x21: ffff0820abfe3880 [ 3078.349018] x20: 0000000000000000 x19: ffff08209cd76900 x18: 0000000000000000 [ 3078.358620] x17: 0000000000000000 x16: ffffc816e1727a50 x15: 0000ffff8f4ff930 [ 3078.368895] x14: 0000000000000000 x13: 0000000000000000 x12: 0000259e9dbeb6b4 [ 3078.377987] x11: 0096a8f7e764eb40 x10: 634615ad28d3eab5 x9 : ffffc816ad8885b8 [ 3078.387091] x8 : ffff08209cfc6fb8 x7 : ffff0820ac0da058 x6 : ffff0820a8490344 [ 3078.396356] x5 : 0000000000000140 x4 : 0000000000000003 x3 : ffff08209cd76938 [ 3078.405365] x2 : 0000000000000000 x1 : 0000000000000010 x0 : ffff0820abfe38a0 [ 3078.414657] Call trace: [ 3078.418517] napi_enable+0x80/0x84 [ 3078.424626] hns3_reset_notify_up_enet+0x78/0xd0 [hns3] [ 3078.433469] hns3_reset_notify+0x64/0x80 [hns3] [ 3078.441430] hclge_notify_client+0x68/0xb0 [hclge] [ 3078.450511] hclge_reset_rebuild+0x524/0x884 [hclge] [ 3078.458879] hclge_reset_service_task+0x3c4/0x680 [hclge] [ 3078.467470] hclge_service_task+0xb0/0xb54 [hclge] [ 3078.475675] process_one_work+0x1dc/0x48c [ 3078.481888] worker_thread+0x15c/0x464 [ 3078.487104] kthread+0x160/0x170 [ 3078.492479] ret_from_fork+0x10/0x18 [ 3078.498785] Code: c8027c81 35ffffa2 d50323bf d65f03c0 (d4210000) [ 3078.506889] ---[ end trace 8ebe0340a1b0fb44 ]--- Once hns3_nic_net_open() is excute success, the flag HNS3_NIC_STATE_DOWN will be cleared. So add checking for this flag, directly return when HNS3_NIC_STATE_DOWN is no set. ## Which versions are affected by CVE-2021-47400? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2021-47400? Apply the vendor's patch. ## Is CVE-2021-47400 being exploited? There is no known exploitation of CVE-2021-47400 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-2021-47400 and fix it if it is affected. What it is: CVE-2021-47400 is a high-severity 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-2021-47400 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-2021-47400/ (Markdown: https://insights.sbomify.com/CVE-2021-47400/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47400 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47400 - OSV: https://osv.dev/vulnerability/CVE-2021-47400 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-47400/ Summaries are generated and may contain mistakes; the official description above is the record.