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CVE-2026-80998
net: bnxt: ring the doorbell when SW USO exits early
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-80998 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When a burst of packets is handed down to the driver, the driver defers the doorbell to the end by setting txr->kick_pending = 1. The normal TX path handles this, but the SW USO path can miss it if it returns early. If bnxt_sw_udp_gso_xmit runs but returns early with NETDEV_TX_BUSY and txr->kick_pending was previously set to 1, then the TX queue can stall because the driver wrote some BDs but never wrote the doorbell. The device won't know to do the TX which would generate the completion that would wake the queue back up. Simplify bnxt_sw_udp_gso_xmit to set txr->kick_pending in its success case and check the flag on return. The added check after bnxt_sw_udp_gso_xmit returns ensures that any pending doorbells are written handling both successful USO and any early returns, which prevents the TX queue stall mentioned above. This TX queue stall was observed on a production system with a netdev TX watchdog informing about the queue stall.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/net/ethernet/broadcom/bnxt/bnxt.c
drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c
- What this is
- BROADCOM BNXT_EN 50 GIGABIT ETHERNET DRIVERMAINTAINERS section matched on drivers/net/ethernet/broadcom/bnxt/ · netdev@vger.kernel.org · Maintained
- Kernel module
- bnxt_en
Check it on the machine
grep -wE 'CONFIG_BNXT|CONFIG_ETHERNET|CONFIG_NET_VENDOR_BROADCOM' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w bnxt_enPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armel/rpi
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_BNXT, CONFIG_ETHERNET, CONFIG_NET_VENDOR_BROADCOM
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-11 (37 days ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.49%, higher than 40.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 7.1 | 7.2.4 | 48d1c9665db6 |
| 7.1 | 7.3 | 4e15e89faac9 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The flaw is in bnxt_start_xmit (ndo_start_xmit) on Broadcom NetXtreme NICs; a remote attacker can induce software UDP GSO egress via QUIC/HTTP3 replies, forwarded or bridged tenant flows, or hypervisor uplink transmit on internet-facing cloud and datacenter servers without local shell access.
- AC:LAttack complexity, low
- An attacker can drive a TX burst that sets kick_pending and then a UDP GSO skb that returns NETDEV_TX_BUSY by flooding mixed-size UDP/GSO traffic until the ring or inline header slots are full; this is a deterministic missed-doorbell logic bug, not a race or layout condition outside attacker control.
- PR:NPrivileges required, none
- Reaching bnxt_sw_udp_gso_xmit requires only the ability to cause UDP GSO packets to egress an already-up bnxt interface; unauthenticated QUIC/UDP service traffic and forwarded packets hit this path with no local account, capability, or CAP_NET_ADMIN.
- UI:NUser interaction, none
- Exploitation needs only attacker-generated network traffic that produces UDP GSO transmit on a live bnxt uplink; no victim action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- The missed doorbell stalls and resets transmit queues inside the same kernel/netdev authority and does not cross a VM, IOMMU, or sandbox security boundary.
- C:NConfidentiality impact, none
- The defect only skips a TX doorbell write after an early NETDEV_TX_BUSY or drop return from software USO; it does not read packet or kernel memory and yields no information-disclosure primitive.
- I:NIntegrity impact, none
- No buffer overflow, use-after-free, or other memory corruption occurs; previously posted buffer descriptors are simply never kicked, so there is no unauthorized modification or control-flow hijack.
- A:HAvailability impact, high
- Skipping the doorbell leaves posted TX descriptors unprocessed so completions never arrive, the queue stays stopped, and the netdev watchdog calls bnxt_tx_timeout() and bnxt_reset_task(); repeating the pattern sustains a complete loss of connectivity on the affected NIC.