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Fencer Vulns
medium 5.5

CVE-2021-35477 json

In the Linux kernel through 5.13.7, an unprivileged BPF program can obtain sensitive information from kernel memory via a Speculative Store…

published 2021-08-02 5 y ago modified 2026-10-08 31 d ago also EUVD-2021-22119

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

In the Linux kernel through 5.13.7, an unprivileged BPF program can obtain sensitive information from kernel memory via a Speculative Store Bypass side-channel attack because a certain preempting store operation does not necessarily occur before a store operation that has an attacker-controlled value.

Patch / fix

  • linux Debian 14, Debian 13, Debian 12 5.10.46-4

debian advisories DEBIAN-CVE-2021-35477

  • linux Ubuntu 20.04 LTS 5.4.0-90.101
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1059.62
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1057.61
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1055.58
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1007.8
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1049.51
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1063.66
  • linux-gkeop Ubuntu 20.04 LTS 5.4.0-1026.27

ubuntu advisories UBUNTU-CVE-2021-35477

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-rt SLE Micro 5.5 5.14.21-150500.13.82.1
  • kernel-source-rt SLE Micro 5.5 5.14.21-150500.13.82.1
  • kernel-syms SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.83.2
  • kernel-source SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.83.2
  • kernel-default SLES for SAP 12 SP4, SLES 12 SP4-LTSS, SLE Live Patching 12 SP4 +3 more 4.12.14-95.83.2
  • kernel-syms SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-source SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-default SLES for SAP 15, SLES 15-LTSS, SLE Live Patching 15 +3 more 4.12.14-150.78.1

suse advisories SUSE-SU-2025:0229-1SUSE-SU-2021:3972-1SUSE-SU-2021:3969-1SUSE-SU-2021:3935-1SUSE-SU-2021:3929-1SUSE-SU-2021:3876-1

  • kernel-default openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-vanilla openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-kvmsmall openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-zfcpdump openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-syms openSUSE Leap 15.2 5.3.18-lp152.102.1
  • kernel-obs-qa openSUSE Leap 15.2 5.3.18-lp152.102.1
  • kernel-source openSUSE Leap 15.2 5.3.18-lp152.102.1
  • kernel-default openSUSE Leap 15.2 5.3.18-lp152.102.1

opensuse advisories openSUSE-SU-2021:3876-1openSUSE-SU-2021:1477-1openSUSE-SU-2021:3205-1openSUSE-SU-2021:3179-1openSUSE-SU-2021:1271-1

  • kernel CBL-Mariner 2.0 5.10.78.1-1

azure linux advisories AZL-6572

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

  • linux-hardened Arch Linux 5.13.13.hardened1-1
  • linux Arch Linux 5.13.8.arch1-1
  • linux-zen Arch Linux 5.13.8.zen1-1
  • linux-lts Arch Linux 5.10.56-1

arch linux advisories AVG-2234AVG-2255AVG-2256AVG-2257

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-2021-35477 updated cvss 4.4

kernel: BPF program can obtain sensitive information from kernel memory via a speculative store bypass side-channel attack because the technique used by the BPF verifier to manage speculation is unrel

  • 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
    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
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +81 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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
31 d ago

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:P/I:N/A:N

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.