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CVE-2026-68152
amt: fix use-after-free in AMT delayed works
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-68152 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 | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When an AMT device is removed, pending delayed works can still access the freed amt_dev structure, which may result in kernel crashes or memory corruption. amt_dev_stop() cancels req_wq and discovery_wq with cancel_delayed_work_sync(), but these works can be scheduled again from event_wq after the cancellation. This allows delayed works to access the freed amt_dev structure after the netdev has been released. The following is a simple race scenario: CPU0 CPU1 amt_dev_stop() cancel_delayed_work_sync() amt_event_work() mod_delayed_work(req_wq) free netdev req_wq accesses freed amt_dev Use disable_delayed_work_sync() in amt_dev_stop() to prevent req_wq and discovery_wq from being queued again and wait for running work items to complete. The delayed works are disabled after initialization in amt_newlink() and enabled only when the device is successfully opened. This keeps the delayed work lifecycle synchronized with the lifetime of the AMT device.
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/amt.c
- What this is
- AMT (Automatic Multicast Tunneling)MAINTAINERS section matched on drivers/net/amt.c · netdev@vger.kernel.org · Maintained
- Kernel module
- none to look for. The file would have gone into amt, and Debian does not compile it into that module, so finding amt in lsmod would say nothing about this CVE.
Check it on the machine
grep -w CONFIG_AMT /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.
Show whether Debian builds this, per release
Debian does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- Build switch
- CONFIG_AMT
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
- 2026-08-10 (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
- 0.13%, higher than 2.6% 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 |
|---|---|---|
| 5.16 | 6.12.101 | a46bfa01e01d |
| 5.16 | 6.18.42 | 1a644db2cf59 |
| 5.16 | 7.1.6 | 006340cf0688 |
| 5.16 | 7.2 | ea20c44935d6 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | 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
- Exploitation requires triggering amt_dev_stop() via local rtnetlink (RTM_DELLINK/ip link del) or ndo_stop on an AMT gateway netdev; the UAF race in teardown is not reachable by remote UDP alone without this privileged local device-removal path.
- AC:LAttack complexity, low
- The attacker controls both sides of the race by concurrently deleting/bringing down the AMT interface while flooding AMT UDP packets or letting discovery/request timers fire, reliably re-queuing req_wq/discovery_wq via amt_event_work during the cancel_work_sync window.
- PR:LPrivileges required, low
- Creating, opening, and removing AMT virtual interfaces requires CAP_NET_ADMIN via rtnetlink, which unprivileged users can obtain inside a user network namespace (unshare -Urn), but not without any privileges at all.
- UI:NUser interaction, none
- No victim user interaction is required; a single attacker with namespace CAP_NET_ADMIN can create an AMT gateway, bring it up, and race interface teardown against self-generated AMT traffic or delayed-work events.
- S:UScope, unchanged
- Successful exploitation corrupts kernel heap memory and can escalate privileges within the same kernel, but does not inherently cross VM, container, or IOMMU security boundaries into a separate authority domain.
- C:HConfidentiality impact, high
- Use-after-free of the amt_dev structure embedded in netdev private data allows accessing attacker-influenced freed heap memory, enabling arbitrary kernel memory disclosure through standard UAF exploitation techniques.
- I:HIntegrity impact, high
- The UAF on amt_dev delayed-work handlers can corrupt kernel heap metadata and adjacent objects, providing primitives for arbitrary kernel memory writes and potential code execution as acknowledged in the fix commit.
- A:HAvailability impact, high
- Use-after-free in amt_req_work/amt_discovery_work accessing freed amt_dev during netdev teardown can cause kernel oops, panic, or hang, and the fix commit explicitly warns of kernel crashes and memory corruption.