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CVE Record

CVE-2020-27171: An issue was discovered in the Linux kernel before 5.11.8.

An issue was discovered in the Linux kernel before 5.11.8. kernel/bpf/verifier.c has an off-by-one error (with a resultant integer underflow) affecting out-of-bounds speculation on pointer arithmetic, leading to side-channel attacks that defeat Spectre mitigations and obtain sensitive information from kernel memory, aka CID-10d2bb2e6b1d.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2020-27171 is a Linux kernel memory disclosure flaw. A local unprivileged user could bypass Spectre-related protections and infer sensitive kernel memory through side channels. This is most urgent on shared Linux systems where local users, workloads, or containers may be less trusted.

Executive priority

Prioritize remediation for shared Linux infrastructure and systems exposed to untrusted local workloads. There is no supplied evidence of active exploitation, but kernel memory disclosure can materially weaken isolation and incident containment.

Technical view

The flaw is an off-by-one error causing integer underflow in kernel/bpf/verifier.c. It affects speculative bounds handling for BPF pointer arithmetic, permitting out-of-bounds speculation and side-channel leakage of kernel memory. Upstream references identify Linux kernels before 5.11.8 and commit 10d2bb2e6b1d as the fix point.

Likely exposure

Exposure is likely on Linux systems running kernels before 5.11.8 or affected downstream vendor kernels before their security updates. Risk depends on whether unprivileged local users or workloads can reach BPF verifier behavior. Fedora and Debian advisories indicate downstream kernel packages required updates.

Exploitation context

The source bundle does not show CISA KEV listing or confirmed active exploitation. Public oss-security discussion describes impact for unprivileged local users, and patch details are public. Treat this as a local post-access information disclosure risk, not a remote unauthenticated compromise based on available evidence.

Researcher notes

Focus validation on kernel lineage and downstream backports rather than version string alone. The provided sources do not include CVSS, CWE, detailed affected product matrices, or exploitation telemetry, so exposure assessment should be vendor-advisory driven.

Mitigation direction

  • Update Linux kernels using vendor security advisories or upstream 5.11.8-or-later fixed code.
  • Prioritize multi-user servers, container hosts, and systems allowing untrusted local code execution.
  • Review Fedora, Debian, and other distribution advisories for backported fixed kernel versions.
  • Check vendor guidance before applying interim controls not named in the sources.

Validation and detection

  • Inventory Linux kernel versions across servers, endpoints, and container hosts.
  • Confirm whether installed vendor kernels include the CVE-2020-27171 fix or backport.
  • Identify systems where untrusted local users or workloads can execute code.
  • Verify patched systems rebooted into the fixed kernel, not only installed it.
Prepared
Confidence
medium
Sources
6

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

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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
8Source 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

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