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Fencer Vulns
critical 9.8

CVE-2026-43376 in the critical feed json

ksmbd: fix use-after-free by using call_rcu() for oplock_info

published 2026-05-08 6 mo ago modified 2026-08-05 3 mo ago also EUVD-2026-28682

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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

ksmbd: fix use-after-free by using call_rcu() for oplock_info

ksmbd currently frees oplock_info immediately using kfree(), even though it is accessed under RCU read-side critical sections in places like opinfo_get() and proc_show_files().

Since there is no RCU grace period delay between nullifying the pointer and freeing the memory, a reader can still access oplock_info structure after it has been freed. This can leads to a use-after-free especially in opinfo_get() where atomic_inc_not_zero() is called on already freed memory.

Fix this by switching to deferred freeing using call_rcu().

Patch / fix

  • Linux Linux 6.6.130, 6.12.78, 6.15, 6.18.19, 6.19.9, 7.0
  • linux Debian 13 6.12.85-1
  • linux Debian 14 6.19.10-1

debian advisories DEBIAN-CVE-2026-43376

  • linux Ubuntu 25.10 6.17.0-40.40
  • linux-aws Ubuntu 25.10 6.17.0-1019.19
  • linux-gcp Ubuntu 25.10 6.17.0-1020.22
  • linux-raspi Ubuntu 25.10 6.17.0-1021.21
  • linux-riscv Ubuntu 25.10 6.17.0-40.40.1
  • linux-oracle Ubuntu 25.10 6.17.0-1018.18
  • linux-aws-6.17 Ubuntu 24.04 LTS 6.17.0-1019.19~24.04.1
  • linux-gcp-6.17 Ubuntu 24.04 LTS 6.17.0-1020.22~24.04.1

ubuntu advisories UBUNTU-CVE-2026-43376

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-2026-43376 updated

kernel: ksmbd: fix use-after-free by using call_rcu() for oplock_info

  • 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

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
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.