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Fencer Vulns
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 2021-06-01 5 y ago modified 2026-06-17 4 mo 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

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, 2026-11-08).

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 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.