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no cvss —

CVE-2026-80808 json

ext4: stop retrying saturated xattr cache entries

published 2mo ago modified 5d ago also EUVD-2026-71243

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

Summary

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

ext4: stop retrying saturated xattr cache entries

ext4_xattr_block_set() retries when a cache entry selected for reuse has a saturated reference count after taking the buffer lock. The retry returns to the mbcache lookup without making that entry ineligible, so it can select the same unusable entry indefinitely. A task spinning there can hold the parent directory's i_rwsem and leave concurrent rmdir callers blocked.

Normally a reusable entry has a reference count below EXT4_XATTR_REFCOUNT_MAX because the count and MBE_REUSABLE_B are updated under the same buffer lock. A corrupted filesystem can violate that invariant. The syzbot reproducer reports allocator and xattr corruption before triggering this retry loop.

Check the untrusted on-disk count before incrementing it, avoiding overflow, and clear MBE_REUSABLE_B when it is already saturated. The next lookup then skips the entry that was just proven unusable. This mirrors the normal transition at EXT4_XATTR_REFCOUNT_MAX; the release path marks the entry reusable again on the exact 1024-to-1023 transition.

Using the same QEMU harness and guest parameters, current unpatched Linux hung in 6 of 8 420-second trials with the do_rmdir signature; representative NMI backtraces caught the owner spinning in ext4_xattr_block_set(). The patched kernel completed 28 of 28 trials without a hung-task report; the final twelve trials exercised the reviewed overflow-safe form of the change. syzbot's patch testing also completed without reproducing the hang.

Patch / fix

  • Linux Linux 4.20, 5.5, 5.10.267, 5.15.218, 5.19, 5.20, 6.1.185, 6.6.154, 6.12.106, 6.18.47, 7.1.11, 7.2.1, 7.3
  • linux Debian 12 6.1.187-1
  • linux Debian 13 6.12.107-1
  • linux Debian 14 7.1.12-1
  • linux-6.12 Debian 12 6.12.107-1~deb12u1

debian advisories DEBIAN-CVE-2026-80808

  • linux Ubuntu 22.04 LTS 5.15.0-202.212
  • linux Ubuntu 24.04 LTS 6.8.0-149.149
  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1119.126
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1069.74
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1120.130
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1073.81

ubuntu advisories UBUNTU-CVE-2026-80808

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

  • kernel-source Linux Micro 6.0 6.4.0-159998.55.1
  • kernel-default Linux Micro 6.0 6.4.0-159998.55.1
  • kernel-kvmsmall Linux Micro 6.0 6.4.0-159998.55.1
  • kernel-default-base Linux Micro 6.0 6.4.0-159998.55.1.159998.21.42
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.90.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.90.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.90.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.90.1

suse advisories SUSE-SU-2026:5121-1SUSE-SU-2026:24550-1SUSE-SU-2026:5091-1

  • kernel-source openSUSE Tumbleweed 7.2.5-1.1

opensuse advisories openSUSE-SU-2026:11773-1

  • kernel Azure Linux 3.0 6.6.157.1-1

azure linux advisories AZL-99678

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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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-2026-80808 updated cvss 5.5

kernel: ext4: stop retrying saturated xattr cache entries

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • 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 Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8
    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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5d ago

Exploit prediction

0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-11).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Intel 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.