CVE-2025-39894 — netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm

When send a broadcast packet to a tap device, which was added to a bridge, br_nf_local_in() is called to confirm the conntrack. If another conntrack with the same hash value is added to the hash table, which can be triggered by a normal packet to a non-bridge device, the below warning may happen.

------------[ cut here ]------------ WARNING: CPU: 1 PID: 96 at net/bridge/br_netfilter_hooks.c:632 br_nf_local_in+0x168/0x200 CPU: 1 UID: 0 PID: 96 Comm: tap_send Not tainted 6.17.0-rc2-dirty #44 PREEMPT(voluntary) RIP: 0010:br_nf_local_in+0x168/0x200 Call Trace: <TASK> nf_hook_slow+0x3e/0xf0 br_pass_frame_up+0x103/0x180 br_handle_frame_finish+0x2de/0x5b0 br_nf_hook_thresh+0xc0/0x120 br_nf_pre_routing_finish+0x168/0x3a0 br_nf_pre_routing+0x237/0x5e0 br_handle_frame+0x1ec/0x3c0 __netif_receive_skb_core+0x225/0x1210 __netif_receive_skb_one_core+0x37/0xa0 netif_receive_skb+0x36/0x160 tun_get_user+0xa54/0x10c0 tun_chr_write_iter+0x65/0xb0 vfs_write+0x305/0x410 ksys_write+0x60/0xd0 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> ---[ end trace 0000000000000000 ]---

To solve the hash conflict, nf_ct_resolve_clash() try to merge the conntracks, and update skb->_nfct. However, br_nf_local_in() still use the old ct from local variable 'nfct' aft…

USN-7909-1 — linux, linux-aws, linux-aws-5.15, linux-gcp-5.15, linux-hwe-5.15, linux-ibm, linux-ibm-5.15, linux-intel-iotg, linux-in…

Affected: Ubuntu:Pro:20.04:LTS: linux-aws-5.15, Ubuntu:Pro:20.04:LTS: linux-gcp-5.15, Ubuntu:Pro:20.04:LTS: linux-hwe-5.15, Ubuntu:Pro:20.04:LTS: linux-ibm-5.15, Ubuntu:Pro:20.04:LTS: linux-intel-iotg-5.15, Ubuntu:Pro:20.04:LTS: linux-lowlatency-hwe-5.15, Ubuntu:Pro:20.04:LTS: linux-nvidia-tegra-5.15, Ubuntu:Pro:20.04:LTS: linux-oracle-5.15, Ubuntu:22.04:LTS: linux, Ubuntu:22.04:LTS: linux-aws and 8 more

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - ARM32 architecture; - ARM64 architecture; - MIPS architecture; - PowerPC architecture; - RISC-V architecture; - S390 architecture; - x86 architecture; - Block layer subsystem; - ACPI drivers; - ATM drivers; - DRBD Distributed Replicated Block Device drivers; - Bus devices; - Clock framework and drivers; - Data acquisition framework and drivers; - Hardware crypto device drivers; - Device frequency scaling framework; - Buffer Sharing and Synchronization framework; - DMA engine subsystem; - ARM SCMI message protocol; - GPU drivers; - HID subsystem; - Hardware monitoring drivers; - I2C subsystem; - I3C subsystem; - IIO subsystem; - InfiniBand drivers; - Input Device core drivers; - IOMMU subsystem; - Media drivers; - Network drivers; - Mellanox network drivers; - PCI subsystem; - PCCARD (PCMCIA/CardBus) bus subsystem; - PHY drivers; - Power supply drivers; - Voltage and Current Regulator drivers; - SCSI subsystem; - ASPEED SoC drivers; - QCOM SoC drivers; - small TFT LCD display modules; - Trusted Execution Environment drivers; - TTY drivers; - UFS subsystem; - USB core drivers; - DesignWare USB3 driver; - USB Gadget drivers; - Framebuffer layer; - BTRFS file system; - File systems infrastructure; - EF…

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CVE-2025-39894 — netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm

USN-7909-1 — linux, linux-aws, linux-aws-5.15, linux-gcp-5.15, linux-hwe-5.15, linux-ibm, linux-ibm-5.15, linux-intel-iotg, linux-in…