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CVE Record

CVE-2021-36087: The CIL compiler in SELinux 3.2 has a heap-based buffer over-read in ebitmap_match_any (called indirectly f...

The CIL compiler in SELinux 3.2 has a heap-based buffer over-read in ebitmap_match_any (called indirectly from cil_check_neverallow). This occurs because there is sometimes a lack of checks for invalid statements in an optional block.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-36087 is a memory-read bug in the SELinux CIL compiler. A malformed CIL policy optional block can trigger a heap-based over-read during neverallow checks. The business risk is most relevant where systems compile SELinux policy from supplied or automated inputs.

Executive priority

Treat as a targeted maintenance item unless your environment compiles SELinux policy from untrusted or semi-trusted sources. Escalate for security engineering review in automated policy-generation, appliance, or multi-tenant management contexts.

Technical view

The issue is in SELinux 3.2 CIL compiler logic: ebitmap_match_any is reached indirectly from cil_check_neverallow without sufficient validation of invalid statements in optional blocks. Public sources identify an upstream SELinux commit and downstream Fedora, Debian LTS, and NetApp advisories, but the bundle provides no CVSS score.

Likely exposure

Exposure is likely limited to environments using affected SELinux CIL compiler components, especially policy build pipelines or products that process CIL policy. The provided affected-product metadata is incomplete, so confirm through vendor package advisories rather than product names alone.

Exploitation context

The bundle does not show CISA KEV listing or other evidence of active exploitation. OSS-Fuzz references suggest discovery through fuzz testing. Public evidence supports a malformed-input crash or memory safety concern, but not real-world exploitation.

Researcher notes

Key evidence points are the CVE description, OSS-Fuzz record, SELinux mailing-list discussion, upstream commit 340f0eb7f3673e8aacaf0a96cbfcd4d12a405521, and downstream advisories. Affected-product metadata is sparse, so package-level confirmation is required.

Mitigation direction

  • Check vendor advisories for affected SELinux or libsepol packages.
  • Update to vendor-fixed SELinux policy compiler packages where available.
  • Confirm whether Fedora, Debian LTS, or NetApp guidance applies.
  • Restrict CIL policy compilation inputs to trusted administrators and pipelines.
  • Prioritize sooner if untrusted users can submit policy content.

Validation and detection

  • Inventory systems and products that compile SELinux CIL policy.
  • Confirm installed packages include the upstream fix or vendor backport.
  • Review policy build workflows for externally supplied CIL input.
  • Track vendor advisories until all applicable platforms are addressed.
Prepared
Confidence
medium
Sources
9

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

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CVE-2021-36087 mapping review

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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

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