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CVE-2025-39810
bnxt_en: Fix memory corruption when FW resources change during ifdown
Published 2025-09-16 (13 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2025-39810 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6008-1 · 2025-09-22 · text | 6.12.48-1 | Update the kernel and reboot. DSA-6008-1 shipped the fix on 2025-09-22, in 6.12.48-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 6.16.5-1 | Update the kernel and reboot. Fixed in 6.16.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.16.5-1 | Update the kernel and reboot. Fixed in 6.16.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
bnxt_set_dflt_rings() assumes that it is always called before any TC has been created. So it doesn't take bp->num_tc into account and assumes that it is always 0 or 1. In the FW resource or capability change scenario, the FW will return flags in bnxt_hwrm_if_change() that will cause the driver to reinitialize and call bnxt_cancel_reservations(). This will lead to bnxt_init_dflt_ring_mode() calling bnxt_set_dflt_rings() and bp->num_tc may be greater than 1. This will cause bp->tx_ring[] to be sized too small and cause memory corruption in bnxt_alloc_cp_rings(). Fix it by properly scaling the TX rings by bp->num_tc in the code paths mentioned above. Add 2 helper functions to determine bp->tx_nr_rings and bp->tx_nr_rings_per_tc.
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
- 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
- 2025-09-16 (13 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- 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 |
|---|---|---|
| 5.4 | 6.12.45 | d00e98977ef5 |
| 5.4 | 6.16.5 | 9ab6a9950f15 |
| 5.4 | 6.17 | 2747328ba271 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6008-1 | 2025-09-22 | trixie 6.12.48-1 | tracker |
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:LAttack vector, local
- The trigger sequence is local device configuration — mqprio/DCBNL to set `bp->num_tc > 1` via rtnetlink, then a link down/up cycle through `bnxt_open()`. No remote peer traffic or network protocol data reaches the vulnerable computation.
- AC:LAttack complexity, low
- The attacker arms the condition persistently: once multi-TC is configured, every subsequent ifup that sees a firmware `RESC_CHANGE`/`CAPS_CHANGE` deterministically undersizes `bp->tx_ring[]`, and such resource changes are routine recurring events (SR-IOV VF count changes, RoCE driver load/unload, firmware update, PF reconfiguration) that can simply be waited out and re-triggered by cycling the interface — there is no one-shot race to win.
- PR:LPrivileges required, low
- Reaching the path needs CAP_NET_ADMIN over the bnxt netdev, which in the common SR-IOV cloud/Kubernetes deployment is held by an otherwise unprivileged container after a VF is delegated into its user-namespace-owned network namespace, where `tc qdisc add ... mqprio` and `ip link set up` are permitted. That is delegated network-admin capability, not real root in the init namespace.
- UI:NUser interaction, none
- No victim action is needed — the corruption occurs entirely within the attacker's own interface bring-up sequence once the multi-TC configuration is in place.
- S:UScope, unchanged
- The out-of-bounds write corrupts kernel heap objects belonging to the same kernel security authority; no VM, IOMMU, or hypervisor boundary is crossed.
- C:HConfidentiality impact, high
- The overflow plants live `bnxt_cp_ring_info` pointers into adjacent heap objects and leaves `netdev_set_tc_queue()` mappings pointing past `real_num_tx_queues`, so subsequent TX-completion and queue-selection code dereferences and reads memory outside the intended objects, which is leverageable for kernel memory disclosure.
- I:HIntegrity impact, high
- `bp->tx_ring[n].tx_cpr = cpr2` writes a kernel heap pointer well beyond the `kcalloc`'d array, at an offset scaled by the attacker-chosen `num_tc` and per-TC ring count — a placement-influenceable arbitrary-ish pointer write into neighbouring slab objects, the classic primitive for control-flow hijack.
- A:HAvailability impact, high
- Corrupting unrelated heap allocations with stray pointers, plus TX queues indexed past `real_num_tx_queues`, reliably produces oops/panic on a machine performing normal networking, and the sequence can be repeated at will.