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Fencer Vulns
high 8.8

CVE-2026-31735 json

iommupt: Fix short gather if the unmap goes into a large mapping

published 2026-05-01 6 mo ago modified 2026-08-05 3 mo ago also EUVD-2026-26548

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

iommupt: Fix short gather if the unmap goes into a large mapping

unmap has the odd behavior that it can unmap more than requested if the ending point lands within the middle of a large or contiguous IOPTE.

In this case the gather should flush everything unmapped which can be larger than what was requested to be unmapped. The gather was only flushing the range requested to be unmapped, not extending to the extra range, resulting in a short invalidation if the caller hits this special condition.

This was found by the new invalidation/gather test I am adding in preparation for ARMv8. Claude deduced the root cause.

As far as I remember nothing relies on unmapping a large entry, so this is likely not a triggerable bug.

Patch / fix

  • Linux Linux 6.19.12, 7.0
  • linux Debian 14 6.19.12-1

debian advisories DEBIAN-CVE-2026-31735

  • linux-nvidia Ubuntu 26.04 LTS 7.0.0-1006.6

ubuntu advisories UBUNTU-CVE-2026-31735

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-31735 updated cvss 5.5

kernel: iommupt: Fix short gather if the unmap goes into a large mapping

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.