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CVE-2026-74725
enic: fix tx_hang_reset use-after-free on device removal
Published 2026-08-22 (2 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-2026-74725 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-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
enic_remove() cancels the reset and change_mtu_work items but does not cancel tx_hang_reset. A TX timeout that fires while the device is being removed can schedule enic_tx_hang_reset() so that it runs after free_netdev(), resulting in a use-after-free. cancel_work_sync() alone is not sufficient here: the still-live watchdog and notify paths can re-schedule these work items in the window between the cancel and unregister_netdev(). Use disable_work_sync(), which cancels the work and blocks any subsequent schedule_work() from requeuing it, and apply it to the reset and change_mtu_work items as well so the same requeue race is closed for all teardown work.
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/cisco/enic/enic_main.c
- What this is
- CISCO VIC ETHERNET NIC DRIVERMAINTAINERS section matched on drivers/net/ethernet/cisco/enic/ · Maintained
- Kernel module
- enic
Check it on the machine
grep -wE 'CONFIG_ENIC|CONFIG_ETHERNET|CONFIG_NET_VENDOR_CISCO' /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 enicPrints 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, sid, bookworm · linux-6.12Mnot 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_ENIC, CONFIG_ETHERNET, CONFIG_NET_VENDOR_CISCO
- 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
- 2026-08-22 (2 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
- 0.12%, higher than 2.0% 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 |
|---|---|---|
| 4.4 | 6.12.104 | 8619865f34fb |
| 4.4 | 6.18.45 | e506e704b747 |
| 4.4 | 7.1.9 | 4f3464fc6c1f |
| 4.4 | 7.2 | ec680ea4ba1b |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | 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 UAF occurs during enic_remove() PCI/driver teardown (sysfs unbind, rmmod, or hot-unplug); TX timeout is raised by the local netdev watchdog, not by remote packet processing, and there is no standalone network path into enic_remove itself.
- AC:LAttack complexity, low
- This is a workqueue race during removal: once teardown starts the netdev can still be up so the watchdog schedules enic_tx_hang_reset, and an attacker can reliably drive TX timeout by stalling or flooding xmit on the still-registered interface while removal proceeds.
- PR:LPrivileges required, low
- PCI unbind/module unload needs elevated privileges, but an unprivileged local or tenant workload can supply the concurrent netdev watchdog TX timeout (local/remote traffic on the Cisco VIC uplink) that schedules tx_hang_reset; per driver-removal UAF precedent, PR:L.
- UI:NUser interaction, none
- No victim interaction is required beyond routine driver removal, module unload, or hypervisor VNIC hot-unplug; monitoring and network traffic on the live interface can schedule tx_hang_reset during teardown without cooperation.
- S:UScope, unchanged
- Impact is use-after-free of netdev_priv enic memory in the host/guest kernel, enabling crash or privilege escalation within the same kernel security authority; it does not cross VM, hypervisor, IOMMU, or container boundaries.
- C:HConfidentiality impact, high
- enic_tx_hang_reset dereferences freed enic/netdev memory via container_of(work, struct enic, tx_hang_reset); UAF on the unified netdev slab enables arbitrary kernel memory disclosure once the object is reallocated.
- I:HIntegrity impact, high
- The scheduled work performs hang reset, stop/open, and notifier calls through the dangling enic pointer, giving attacker-influenced writes and control-flow hijack primitives typical of netdev driver UAF exploitation.
- A:HAvailability impact, high
- Use-after-free during enic_tx_hang_reset reliably causes kernel oops/panic when the work runs after free_netdev(), and even attempted exploitation crashes the system on dangling enic/netdev accesses.