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CVE-2026-68140
net/iucv: fix use-after-free of a severed iucv_path
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem net/iucv. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68140 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| 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
af_iucv queues not-yet-received message notifications on iucv->message_q, each holding a raw pointer to the connection's iucv_path. When the peer severs the connection, iucv_sever_path() frees that path with iucv_path_free() but leaves the notifications queued. A later recvmsg() drains message_q via iucv_process_message_q() and hands the stale path to message_receive() -- a use-after-free of the freed iucv_path. Drop the queued notifications when the path is severed; once the path is gone they can no longer be received. This also frees the notifications leaked when a socket is closed with messages still queued.
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/iucv/af_iucv.c
- What this is
- S390 IUCV NETWORK LAYERMAINTAINERS section matched on net/iucv/ · linux-s390@vger.kernel.org · Supported
- Kernel module
- af_iucv
Check it on the machine
grep -wE 'CONFIG_AFIUCV|CONFIG_IUCV' /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 af_iucvPrints 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 does not build this code in 2 releases. It does build it in 3 releases, so the answer depends on which release the machine runs.
- bookwormn
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, 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
- forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, 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
- bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_AFIUCV, CONFIG_IUCV
- 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
- 2026-08-10 (2 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.27%, higher than 18.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/iucv
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.24 | 5.10.265 | 5f08c5e50bcb |
| 2.6.24 | 5.15.216 | c24faf11bd31 |
| 2.6.24 | 6.1.183 | 99ddb3374869 |
| 2.6.24 | 6.6.148 | 23658b350b41 |
| 2.6.24 | 6.12.101 | a5bbaddf6985 |
| 2.6.24 | 6.18.42 | 900cd6d8119b |
| 2.6.24 | 7.1.6 | f579582c03ed |
| 2.6.24 | 7.2 | be7cc4656eb1 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| 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:AAttack vector, adjacent network
- An adjacent z/VM guest or LPAR peer can establish an AF_IUCV connection and deliver IUCV message_pending and path_severed events to a victim; exploitation requires same-CPC IUCV reachability, not Internet-wide access.
- AC:LAttack complexity, low
- The attacker deterministically floods IUCV messages to fill message_q, severs the connection to free iucv_path, then victim recvmsg() drains the stale queue; no uncontrollable timing or memory-layout luck is required.
- PR:NPrivileges required, none
- On the victim, no local Linux account or capability is needed; any unauthorized adjacent IUCV peer that completes the AF_IUCV handshake can flood messages and sever the path against a listening service.
- UI:NUser interaction, none
- No special victim action is required beyond normal server recvmsg() on an established IUCV session; the attacker drives connection setup, message flood, and path sever entirely from the peer side.
- S:UScope, unchanged
- Impact is kernel memory corruption within the victim Linux guest; it does not cross hypervisor, VM-escape, or IOMMU security boundaries.
- C:HConfidentiality impact, high
- Queued notifications dereference a freed struct iucv_path in message_receive(), passing stale pathid and private fields into CP IUCV RECEIVE calls—a classic UAF enabling attacker-controlled heap reuse and kernel memory disclosure.
- I:HIntegrity impact, high
- Use-after-free of iucv_path lets an attacker reclaim the freed object and supply forged pathid and list pointers used by __iucv_message_receive(), providing heap corruption primitives suitable for arbitrary kernel write or code execution.
- A:HAvailability impact, high
- Processing the stale path in iucv_process_message_q() dereferences freed kernel memory during message_receive(), reliably causing kernel oops or panic and total loss of availability even before full exploitation.