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CVE-2026-72291
KVM: s390: Fix unlikely race in try_get_locked_pte()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem arch/s390. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72291 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 | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Fix an unlikely race in try_get_locked_pte(), which could have happened if puds or pmds get unmapped between the p?dp_get() and p?d_offset() functions.
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.
arch/s390/mm/gmap_helpers.c
- What this is
- KERNEL VIRTUAL MACHINE for s390 (KVM/s390)MAINTAINERS section matched on arch/s390/mm/gmap_helpers.c · kvm@vger.kernel.org · Supported
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid?
- ?
- not established - no Makefile entry for the affected file
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.
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
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 9.3 critical
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 7.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- arch/s390
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 7.1 | 7.1.5 | ce587046baac |
| 7.1 | 7.2 | 5670b7f927f8 |
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 flaw is in KVM s390 host page-table walking triggered by local guest hypervisor intercepts (UVC, ESSA) and /dev/kvm ioctls, not by remote network packet handling.
- AC:LAttack complexity, low
- An attacker can control both sides of the race using multiple vCPUs or threads to concurrently trigger KVM gmap unmap/PV operations while host backing mappings are torn down via slot changes or ballooning.
- PR:NPrivileges required, none
- A malicious s390 KVM guest can reach the vulnerable paths through hypervisor instruction intercepts without requiring host administrator privileges or CAP_SYS_ADMIN on the hypervisor.
- UI:NUser interaction, none
- Exploitation requires only attacker-controlled guest execution and concurrent memory management activity, with no additional victim actions such as opening files or mounting filesystems.
- S:CScope, changed
- Corrupting host kernel page tables while servicing guest memory operations crosses the guest-host virtualization security boundary and enables VM escape-class impact on shared IBM Z KVM hosts.
- C:HConfidentiality impact, high
- The race dereferences freed intermediate page-table pages and can yield attacker-influenced PTE pointers, enabling arbitrary kernel memory disclosure through subsequent PTE reads.
- I:HIntegrity impact, high
- Corrupted PTE pointers lead to atomic PTE bit updates and secure-page folio operations on attacker-chosen kernel memory, providing a plausible path to arbitrary write or code execution.
- A:HAvailability impact, high
- Dereferencing freed or collapsed page-table structures or corrupting PTEs can cause kernel oops, panic, or repeated guest-triggered crashes denying host availability.