net: bridge: fix vlan tunnel dst refcnt when egressing
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 4 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.
Summary
In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix vlan tunnel dst refcnt when egressing The egress tunnel code uses dst_clone() and directly sets the result which is wrong because the entry might have 0 refcnt or be already deleted, causing number of problems. It also triggers the WARN_ON() in dst_hold()[1] when a refcnt couldn't be taken. Fix it by using dst_hold_safe() and checking if a reference was actually taken before setting the dst. [1] dmesg WARN_ON log and following refcnt errors WARNING: CPU: 5 PID: 38 at include/net/dst.h:230 br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge] Modules linked in: 8021q garp mrp bridge stp llc bonding ipv6 virtio_net CPU: 5 PID: 38 Comm: ksoftirqd/5 Kdump: loaded Tainted: G W 5.13.0-rc3+ #360 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014 RIP: 0010:br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge] Code: e8 85 bc 01 e1 45 84 f6 74 90 45 31 f6 85 db 48 c7 c7 a0 02 19 a0 41 0f 94 c6 31 c9 31 d2 44 89 f6 e8 64 bc 01 e1 85 db 75 02 <0f> 0b 31 c9 31 d2 44 89 f6 48 c7 c7 70 02 19 a0 e8 4b bc 01 e1 49 RSP: 0018:ffff8881003d39e8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffa01902a0 RBP: ffff8881040c6700 R08: 0000000000000000 R09: 0000000000000001 R10: 2ce93d0054fe0d00 R11: 54fe0d00000e0000 R12: ffff888109515000 R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000401 FS: 0000000000000000(0000) GS:ffff88822bf40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f42ba70f030 CR3: 0000000109926000 CR4: 00000000000006e0 Call Trace: br_handle_vlan+0xbc/0xca [bridge] __br_forward+0x23/0x164 [bridge] deliver_clone+0x41/0x48 [bridge] br_handle_frame_finish+0x36f/0x3aa [bridge] ? skb_dst+0x2e/0x38 [bridge] ? br_handle_ingress_vlan_tunnel+0x3e/0x1c8 [bridge] ? br_handle_frame_finish+0x3aa/0x3aa [bridge] br_handle_frame+0x2c3/0x377 [bridge] ? __skb_pull+0x33/0x51 ? vlan_do_receive+0x4f/0x36a ? br_handle_frame_finish+0x3aa/0x3aa [bridge] __netif_receive_skb_core+0x539/0x7c6 ? __list_del_entry_valid+0x16e/0x1c2 __netif_receive_skb_list_core+0x6d/0xd6 netif_receive_skb_list_internal+0x1d9/0x1fa gro_normal_list+0x22/0x3e dev_gro_receive+0x55b/0x600 ? detach_buf_split+0x58/0x140 napi_gro_receive+0x94/0x12e virtnet_poll+0x15d/0x315 [virtio_net] __napi_poll+0x2c/0x1c9 net_rx_action+0xe6/0x1fb __do_softirq+0x115/0x2d8 run_ksoftirqd+0x18/0x20 smpboot_thread_fn+0x183/0x19c ? smpboot_unregister_percpu_thread+0x66/0x66 kthread+0x10a/0x10f ? kthread_mod_delayed_work+0xb6/0xb6 ret_from_fork+0x22/0x30 ---[ end trace 49f61b07f775fd2b ]--- dst_release: dst:00000000c02d677a refcnt:-1 dst_release underflow
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 4.11 and later | 4.14.238, 4.19.196, 5.4.128, 5.10.46, 5.12.13, 5.13 | Patch available | CNA |
- Linux VendorLinux Affected 4.11 and later Fixed in 4.14.238, 4.19.196, 5.4.128, 5.10.46, 5.12.13, 5.13 Patch available CNA
CPE configurations NVD · 7
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 4.11 to before 4.14.238; 4.15 to before 4.19.196; 4.20 to before 5.4.128; 5.5 to before 5.10.46; 5.11 to before 5.12.13 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:* | 5.13 rc1 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:5.13:rc2:*:*:*:*:*:* | 5.13 rc2 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:5.13:rc3:*:*:*:*:*:* | 5.13 rc3 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:5.13:rc4:*:*:*:*:*:* | 5.13 rc4 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:5.13:rc5:*:*:*:*:*:* | 5.13 rc5 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:5.13:rc6:*:*:*:*:*:* | 5.13 rc6 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 4.11 to before 4.14.238; 4.15 to before 4.19.196; 4.20 to before 5.4.128; 5.5 to before 5.10.46; 5.11 to before 5.12.13 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:* Versions 5.13 rc1 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:5.13:rc2:*:*:*:*:*:* Versions 5.13 rc2 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:5.13:rc3:*:*:*:*:*:* Versions 5.13 rc3 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:5.13:rc4:*:*:*:*:*:* Versions 5.13 rc4 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:5.13:rc5:*:*:*:*:*:* Versions 5.13 rc5 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:5.13:rc6:*:*:*:*:*:* Versions 5.13 rc6 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 4.14.238, 4.19.196, 5.4.128, 5.10.46, 5.12.13, 5.13
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
Timeline
- 2026-10-02 Threatist record created from CVE-2021-47222
- 2026-10-03 Alias added: GHSA-h423-6g7m-qpqq
References
Patch 6
- https://git.kernel.org/stable/c/42020f7f37a90d24b9551f5f7eba3f7c7c102968
- https://git.kernel.org/stable/c/84fc1c944e45ab317e2e70a0e7f76fa2a5e43b6e
- https://git.kernel.org/stable/c/79855be6445b6592bddb7bd7167083ec8cdbd73f
- https://git.kernel.org/stable/c/fc7fdd8c5c2ad2fe3e297698be9d4dbe4a4e0579
- https://git.kernel.org/stable/c/25053a8404ba17ca48f5553d487afc1882e9f56c
- https://git.kernel.org/stable/c/cfc579f9d89af4ada58c69b03bcaa4887840f3b3
More Linux Kernel vulnerabilities
- TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
- TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
- TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
- TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
- TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
- TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
Sources
- CVE-2021-47222 · CVE Program
- CVE-2021-47222 · NVD
- FIRST EPSS
- GHSA-h423-6g7m-qpqq · GitHub Advisory Database · CC BY 4.0
- CVE-2021-47222 · Red Hat security data · CC BY 4.0
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