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Fencer Intel
medium 6.7

CVE-2021-3543 json

A flaw null pointer dereference in the Nitro Enclaves kernel driver was found in the way that Enclaves VMs forces closures on the enclave f…

published 5y ago modified 4mo ago also EUVD-2021-26854

cvss
6.7
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits
0
none known

Summary

A flaw null pointer dereference in the Nitro Enclaves kernel driver was found in the way that Enclaves VMs forces closures on the enclave file descriptor. A local user of a host machine could use this flaw to crash the system or escalate their privileges on the system.

Patch / fix

  • nitro_enclaves_project nitro_enclaves 5.10.0
  • linux Debian 14, Debian 13, Debian 12 5.10.38-1

debian advisories DEBIAN-CVE-2021-3543

  • linux-aws Ubuntu 20.04 LTS 5.4.0-1064.67
  • linux-aws-5.4 Ubuntu 18.04 LTS 5.4.0-1064.67~18.04.1
  • linux-oem-5.10 Ubuntu 20.04 LTS 5.10.0-1032.33

ubuntu advisories UBUNTU-CVE-2021-3543

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 RHEL 8 4.18.0-305.3.1.el8_4
  • perf RHEL 8 4.18.0-305.3.1.el8_4
  • bpftool RHEL 8 4.18.0-305.3.1.el8_4
  • kernel-core RHEL 8 4.18.0-305.3.1.el8_4
  • kernel-tools RHEL 8 4.18.0-305.3.1.el8_4
  • python3-perf RHEL 8 4.18.0-305.3.1.el8_4
  • kernel-modules RHEL 8 4.18.0-305.3.1.el8_4
  • kernel-zfcpdump RHEL 8 4.18.0-305.3.1.el8_4

red hat advisories RHSA-2021:2168RHSA-2021:2169

  • kernel Rocky Linux 8 4.18.0-305.3.1.el8_4

rocky linux advisories RLSA-2021:2168

  • linux-lts Arch Linux 5.10.36-1
  • linux Arch Linux 5.12.3.arch1-1
  • linux-zen Arch Linux 5.12.3.zen1-1
  • linux-hardened Arch Linux 5.11.20.hardened1-1

arch linux advisories AVG-1942AVG-1952AVG-1953AVG-1954

Is CVE-2021-3543 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2021-3543 updated cvss 6.7

kernel: nitro_enclaves stale file descriptors on failed usercopy

  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-305.3.1.el8_4, kernel-debuginfo-common-aarch64 4.18.0-305.3.1.el8_4, kernel-debuginfo-common-ppc64le 4.18.0-305.3.1.el8_4 Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-305.3.1.el8_4, kernel 4.18.0-305.3.1.el8_4, bpftool 4.18.0-305.3.1.el8_4, kernel-core 4.18.0-305.3.1.el8_4, kernel-tools 4.18.0-305.3.1.el8_4, python3-perf 4.18.0-305.3.1.el8_4, +15 more
    fixed: vendor fix RHSA-2021:2168
  • Red Hat Enterprise Linux Real Time (v. 8) kernel-rt 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-core 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-modules 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-debug-core 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-debug-modules 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-modules-extra 4.18.0-305.3.1.rt7.75.el8_4, +2 more Red Hat Enterprise Linux Real Time for NFV (v. 8) kernel-rt 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-kvm 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-core 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-modules 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-debug-kvm 4.18.0-305.3.1.rt7.75.el8_4, kernel-rt-debug-core 4.18.0-305.3.1.rt7.75.el8_4, +4 more
    fixed: vendor fix RHSA-2021:2169
  • 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, kernel-alt, python-perf, +9 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    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

0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 6.7 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • n/a kernel

Classification

Weakness

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.