LiveActive security incident?Get immediate response
CVE Record

CVE-2021-35477: In the Linux kernel through 5.13.7, an unprivileged BPF program can obtain sensitive information from kerne...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue could let a local unprivileged user running BPF read sensitive kernel memory through a CPU side channel. That makes it mainly a confidentiality risk on shared Linux systems, build hosts, containers, and multi-user servers.

Executive priority

Treat this as a timely kernel patching issue for shared Linux infrastructure. Urgency is lower than remote code execution, but confidentiality impact can matter where untrusted local users or workloads coexist.

Technical view

Linux kernels through 5.13.7 are described as vulnerable when unprivileged BPF programs interact with Speculative Store Bypass behavior. The issue involves store ordering where an attacker-controlled value may affect a side-channel path before a protective store occurs.

Likely exposure

Exposure is most likely on Linux systems running kernels through 5.13.7 or older vendor kernels without the relevant backports, especially where unprivileged BPF is available to local users or workloads.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation evidence. The described attack is local and side-channel based; it requires the ability to run an unprivileged BPF program, not just remote network access.

Researcher notes

Evidence is strongest for upstream Linux and listed distro advisories. The bundle lacks CVSS, CWE, and detailed affected CPEs, so validate against vendor backport status rather than upstream version alone.

Mitigation direction

  • Update Linux kernel packages using applicable vendor security advisories.
  • Confirm distro kernels include the referenced upstream fixes or backports.
  • Review whether unprivileged BPF can be restricted until patched.
  • Follow Linux vendor guidance for your exact kernel branch.

Validation and detection

  • Inventory Linux kernel versions across servers, containers, and build hosts.
  • Check whether affected systems allow unprivileged BPF use.
  • Verify Fedora, Debian, or vendor advisory fixes are installed.
  • Prioritize shared or multi-tenant Linux systems for confirmation.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2021-35477 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.