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CVE Record

CVE-2021-47336: smackfs: restrict bytes count in smk_set_cipso()

In the Linux kernel, the following vulnerability has been resolved: smackfs: restrict bytes count in smk_set_cipso() Oops, I failed to update subject line. From 07571157c91b98ce1a4aa70967531e64b78e8346 Mon Sep 17 00:00:00 2001 Date: Mon, 12 Apr 2021 22:25:06 +0900 Subject: [PATCH] smackfs: restrict bytes count in smk_set_cipso() Commit 7ef4c19d245f3dc2 ("smackfs: restrict bytes count in smackfs write functions") missed that count > SMK_CIPSOMAX check applies to only format == SMK_FIXED24_FMT case.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-47336 is a Linux kernel Smack filesystem bug involving overly broad byte-count handling in CIPSO configuration writes. The public record gives no CVSS score and no evidence of active exploitation. Business urgency depends on whether affected Linux kernels are used with Smack enabled.

Executive priority

Treat as a targeted Linux kernel maintenance item unless Smack is broadly used in production. Prioritize validation on hardened or embedded Linux systems where Smack may be enabled. Lack of severity data and exploitation evidence prevents a stronger emergency rating.

Technical view

The issue is in smackfs smk_set_cipso(). A prior count restriction missed that the count > SMK_CIPSOMAX check should apply only to the SMK_FIXED24_FMT case. Kernel stable commits are provided as fixes across maintained branches. The sources do not describe remote reachability, exploit primitives, or impact detail beyond the kernel resolution text.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions with Smack and smackfs CIPSO configuration paths in use. The source bundle lists affected Linux versions including 3.5 and several stable branch levels through 5.14. Distribution backports may change apparent version exposure.

Exploitation context

The bundle provides no KEV listing, no exploit report, and no public exploitation claim. Because this is a kernel smackfs write-path flaw, practical exposure likely depends on local access and permissions to interact with Smack configuration, but the sources do not state required privileges.

Researcher notes

The available evidence is sparse. The key technical clue is the conditional scope of SMK_CIPSOMAX enforcement in smk_set_cipso(). Researchers should compare local vendor kernel sources against the stable commits rather than relying only on version strings.

Mitigation direction

  • Update to a vendor kernel containing the referenced stable fix.
  • Check Linux distribution advisories for backported fixes.
  • Prioritize systems using Smack or smackfs CIPSO configuration.
  • Restrict administrative access to smackfs according to vendor guidance.
  • Monitor vendor kernel updates if fixed packages are not yet available.

Validation and detection

  • Inventory Linux kernel versions across affected systems.
  • Confirm whether Smack LSM is enabled on each system.
  • Check whether smackfs is mounted or operationally used.
  • Verify vendor package changelogs include the referenced fix or backport.
  • Review kernel logs for Oops events involving smackfs or CIPSO.
Prepared
Confidence
medium
Sources
10

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-2021-47336 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
3Timeline events
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf7112e6c9abf1c70f001dcf097c1d6e218a93f5c, f7112e6c9abf1c70f001dcf097c1d6e218a93f5c, f7112e6c9abf1c70f001dcf097c1d6e218a93f5c, f7112e6c9abf1c70f001dcf097c1d6e218a93f5c, f7112e6c9abf1c70f001dcf097c1d6e218a93f5c, f7112e6c9abf1c70f001dcf097c1d6e218a93f5c, f7112e6c9abf1c70f001dcf097c1d6e218a93f5c, f7112e6c9abf1c70f001dcf097c1d6e218a93f5cunaffected
LinuxLinux3.5, 0, 4.9.276, 4.14.240, 4.19.198, 5.4.133, 5.10.51, 5.12.18, 5.13.3, 5.14affected
Weakness

CWE details

No CWE listed

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