# CVE-2025-21877: usbnet: gl620a: fix endpoint checking in genelink_bind() > A missing endpoint check in the Linux kernel gl620a USB driver allows a malicious device to trigger a kernel warning and potential 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:** 27 Mar 2025 - **Updated:** 11 May 2026 - **Also known as:** BELL-CVE-2025-21877, DEBIAN-CVE-2025-21877, GHSA-x566-29g2-c4g8, ROOT-OS-UBUNTU-2404-CVE-2025-21877, UBUNTU-CVE-2025-21877 ## What is CVE-2025-21877? CVE-2025-21877 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Mar 2025. 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: usbnet: gl620a: fix endpoint checking in genelink_bind() Syzbot reports [1] a warning in usb_submit_urb() triggered by inconsistencies between expected and actually present endpoints in gl620a driver. Since genelink_bind() does not properly verify whether specified eps are in fact provided by the device, in this case, an artificially manufactured one, one may get a mismatch. Fix the issue by resorting to a usbnet utility function usbnet_get_endpoints(), usually reserved for this very problem. Check for endpoints and return early before proceeding further if any are missing. [1] Syzbot report: usb 5-1: Manufacturer: syz usb 5-1: SerialNumber: syz usb 5-1: config 0 descriptor?? gl620a 5-1:0.23 usb0: register 'gl620a' at usb-dummy_hcd.0-1, ... ------------[ cut here ]------------ usb 5-1: BOGUS urb xfer, pipe 3 != type 1 WARNING: CPU: 2 PID: 1841 at drivers/usb/core/urb.c:503 usb_submit_urb+0xe4b/0x1730 drivers/usb/core/urb.c:503 Modules linked in: CPU: 2 UID: 0 PID: 1841 Comm: kworker/2:2 Not tainted 6.12.0-syzkaller-07834-g06afb0f36106 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Workqueue: mld mld_ifc_work RIP: 0010:usb_submit_urb+0xe4b/0x1730 drivers/usb/core/urb.c:503 ... Call Trace: usbnet_start_xmit+0x6be/0x2780 drivers/net/usb/usbnet.c:1467 __netdev_start_xmit include/linux/netdevice.h:5002 [inline] netdev_start_xmit include/linux/netdevice.h:5011 [inline] xmit_one net/core/dev.c:3590 [inline] dev_hard_start_xmit+0x9a/0x7b0 net/core/dev.c:3606 sch_direct_xmit+0x1ae/0xc30 net/sched/sch_generic.c:343 __dev_xmit_skb net/core/dev.c:3827 [inline] __dev_queue_xmit+0x13d4/0x43e0 net/core/dev.c:4400 dev_queue_xmit include/linux/netdevice.h:3168 [inline] neigh_resolve_output net/core/neighbour.c:1514 [inline] neigh_resolve_output+0x5bc/0x950 net/core/neighbour.c:1494 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0xb1b/0x2070 net/ipv6/ip6_output.c:141 __ip6_finish_output net/ipv6/ip6_output.c:215 [inline] ip6_finish_output+0x3f9/0x1360 net/ipv6/ip6_output.c:226 NF_HOOK_COND include/linux/netfilter.h:303 [inline] ip6_output+0x1f8/0x540 net/ipv6/ip6_output.c:247 dst_output include/net/dst.h:450 [inline] NF_HOOK include/linux/netfilter.h:314 [inline] NF_HOOK include/linux/netfilter.h:308 [inline] mld_sendpack+0x9f0/0x11d0 net/ipv6/mcast.c:1819 mld_send_cr net/ipv6/mcast.c:2120 [inline] mld_ifc_work+0x740/0xca0 net/ipv6/mcast.c:2651 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229 process_scheduled_works kernel/workqueue.c:3310 [inline] worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391 kthread+0x2c1/0x3a0 kernel/kthread.c:389 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 ## Which versions are affected by CVE-2025-21877? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2025-21877? Apply the vendor's patch. ## Is CVE-2025-21877 being exploited? There is no known exploitation of CVE-2025-21877 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-2025-21877 and fix it if it is affected. What it is: CVE-2025-21877 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Mar 2025. 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-2025-21877 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-2025-21877/ (Markdown: https://insights.sbomify.com/CVE-2025-21877/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21877 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21877 - OSV: https://osv.dev/vulnerability/CVE-2025-21877 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-21877/ Summaries are generated and may contain mistakes; the official description above is the record.