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CVE-2026-64115
vsock/vmci: fix UAF when peer resets connection during handshake
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/vmw_vsock. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64115 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 | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
vmci_transport_recv_connecting_server() returned err = 0 for a peer RST in its default switch arm: err = pkt->type == VMCI_TRANSPORT_PACKET_TYPE_RST ? 0 : -EINVAL; That made vmci_transport_recv_listen() skip vsock_remove_pending(), leaving the pending socket on the listener's pending_links with sk_state = TCP_CLOSE while destroy: still dropped the explicit reference taken before schedule_delayed_work(). One second later vsock_pending_work() observed is_pending=true and performed full cleanup: vsock_remove_pending() then the two trailing sock_put(sk) calls -- the first reached refcount 0 and __sk_freed the socket, and the second wrote into the freed object: BUG: KASAN: slab-use-after-free in refcount_warn_saturate Write of size 4 at addr ffff88800b1cac80 by task kworker Workqueue: events vsock_pending_work Treat peer RST like any other unexpected packet type (err = -EINVAL). All destroy: arms now return err < 0, so vmci_transport_recv_listen() removes pending from pending_links synchronously and vsock_pending_work() takes the is_pending=false / !rejected branch, dropping only its own work reference. This also closes the multi-packet race Sashiko reported on v2: pending is removed from the list before any subsequent packet can find it. The pre-existing sk_acceptq_removed() gap on the err < 0 path of vmci_transport_recv_listen() that Sashiko also noted is not introduced or changed by this patch. Tested on lts-6.12.79 with KASAN: 52/100 unpatched -> 0/100 patched.
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.
net/vmw_vsock/vmci_transport.c
- What this is
- VMWARE VSOCK VMCI TRANSPORT DRIVERMAINTAINERS section matched on net/vmw_vsock/vmci_transport* · linux-kernel@vger.kernel.org · Supported
- Kernel module
- vmw_vsock_vmci_transport
Check it on the machine
grep -wE 'CONFIG_VMWARE_VMCI_VSOCKETS|CONFIG_VSOCKETS' /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 vmw_vsock_vmci_transportPrints 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 arm64/arm64, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le
- trixieMnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_VMWARE_VMCI_VSOCKETS, CONFIG_VSOCKETS
- 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
- 2026-07-19 (3 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.14%, higher than 2.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/vmw_vsock
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.9 | 5.10.258 | 1e19f08552b9 |
| 3.9 | 5.15.209 | 1dd531e28f61 |
| 3.9 | 6.1.175 | ecda37f8faab |
| 3.9 | 6.6.142 | cc27e989a5df |
| 3.9 | 6.12.92 | 47e63077605c |
| 3.9 | 6.18.34 | 440447699c68 |
| 3.9 | 7.0.11 | 9fe74e42914c |
| 3.9 | 7.1 | 99e22ddf4edb |
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 local AF_VSOCK syscalls (connect/close) to drive VMCI control packets; per kernel CVSS guidance, vsock is scored Local even when the peer is a VM guest reaching a host listener.
- AC:LAttack complexity, low
- The attacker controls both sides of the handshake race by initiating a connection and aborting it with RST during TCP_SYN_SENT; KASAN testing showed 52/100 repro without conditions outside attacker control.
- PR:LPrivileges required, low
- Any unprivileged local user inside a VM (or on the same host) can open AF_VSOCK sockets and connect to a listening peer without CAP_NET_ADMIN or other elevated privileges.
- UI:NUser interaction, none
- Exploitation requires only a victim service with a bound/listening vsock socket, which is normal background operation; no interactive victim action is needed.
- S:CScope, changed
- In the most severe reasonable VMware deployment, an unprivileged guest VM triggers kernel memory corruption on the hypervisor host via VMCI vsock, crossing the guest-to-host virtualisation security boundary analogous to KVM/Xen VM escape.
- C:HConfidentiality impact, high
- The bug is a slab use-after-free on struct sock; UAF on kernel heap objects enables arbitrary memory read primitives through controlled reuse of the freed socket structure.
- I:HIntegrity impact, high
- The UAF involves a write to a freed object's refcount field and corrupts kernel heap metadata, providing a foundation for arbitrary write and kernel code execution via heap grooming.
- A:HAvailability impact, high
- The vulnerability reliably triggers kernel UAF detected by KASAN (refcount write to freed memory on a kworker), which causes kernel oops/panic and denial of host availability.