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CVE-2026-68134
ptp: ptp_s390: Add missing facility check
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem drivers/ptp. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-68134 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| 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. |
The vulnerability
What the bug is
Only register the physical clock when facility 28 is installed and PTFF QAF returns that PTFF QPT is available.
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/ptp/ptp_s390.c
- What this is
- S390 PTP DRIVERMAINTAINERS section matched on drivers/ptp/ptp_s390.c · linux-s390@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_PTP_S390 /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 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_PTP_S390
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
- 7.3 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/ptp
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.13 | 6.18.42 | b3efb4744abf |
| 6.13 | 7.1.6 | 545a7fdbc110 |
| 6.13 | 7.2 | e78f1ac37afc |
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 bug is reached only via local PTP character-device access: open(/dev/ptpX) followed by ioctl paths such as PTP_SYS_OFFSET or clock_gettime on the posix clock FD, which call ptp_s390_qpt_gettime() and execute the PTFF instruction in kernel context.
- AC:LAttack complexity, low
- On affected IBM Z systems with the s390 PTP driver enabled, any process that can open the physical-clock device can repeatedly issue read ioctls that deterministically invoke PTFF without races or attacker-uncontrollable timing.
- PR:LPrivileges required, low
- PTP read ioctls and clock_gettime do not require CAP_SYS_TIME; on typical chrony/ptp4l and containerized time-sync deployments /dev/ptp* is often opened by non-root service accounts or passed into unprivileged workloads, not only init-namespace root.
- UI:NUser interaction, none
- Exploitation requires only the attacker (or their service account) opening the PTP device and issuing ioctls; no separate victim action such as mounting a filesystem or clicking a prompt is needed.
- S:UScope, unchanged
- Impact is confined to the same Linux kernel running the ptp_s390 driver on the s390 host; it does not cross a VM, IOMMU, or other security boundary to another authority.
- C:HConfidentiality impact, high
- When PTFF QPT is unavailable the driver still calls ptff() and returns the unchecked stack buffer to userspace, leaking kernel memory; on systems without facility 28 the illegal PTFF traps in kernel mode and can expose register/state data during the fault path.
- I:LIntegrity impact, low
- Returning attacker-influenced or uninitialized PTFF output as authoritative PTP time via ioctl can corrupt time-sync decisions for chrony/ptp4l and other consumers that steer system clocks from the physical-clock device.
- A:HAvailability impact, high
- Executing PTFF without facility 28 or on unsupported configurations triggers an s390 program check in kernel context (illegal/specification exception) that ends in die(), causing a kernel oops/panic and total loss of host availability.