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CVE Record

CVE-2021-47086: phonet/pep: refuse to enable an unbound pipe

In the Linux kernel, the following vulnerability has been resolved: phonet/pep: refuse to enable an unbound pipe This ioctl() implicitly assumed that the socket was already bound to a valid local socket name, i.e. Phonet object. If the socket was not bound, two separate problems would occur: 1) We'd send an pipe enablement request with an invalid source object. 2) Later socket calls could BUG on the socket unexpectedly being connected yet not bound to a valid object.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel flaw in the Phonet/PEP networking code. An operation could enable a pipe on a socket that had not been properly bound, leaving the kernel in an invalid state and potentially triggering a kernel BUG. Severity is not scored in the provided sources.

Executive priority

Handle through normal kernel patch management unless local exposure to Phonet/PEP is confirmed. There is no sourced evidence of active exploitation, but kernel BUG conditions can affect availability and should not be ignored on exposed or specialized systems.

Technical view

The affected ioctl path assumed a PEP socket already had a valid local Phonet object. If unbound, it could send a pipe enablement request with an invalid source object and later leave the socket connected without a valid bound object, causing unexpected BUG behavior.

Likely exposure

Exposure is limited to systems running affected Linux kernel versions with Phonet/PEP code present and reachable. The source bundle identifies Linux kernel versions around 3.3 through fixed stable lines including 4.4.297, 4.9.295, 4.14.260, 4.19.223, 5.4.169, 5.10.89, 5.15.12, and 5.16, but range details are incomplete.

Exploitation context

The bundle does not cite active exploitation, public weaponization, CVSS, CWE, or KEV listing. Treat exploitation status as unconfirmed. The described impact is kernel correctness and stability from an invalid unbound socket state, not a documented remote compromise path.

Researcher notes

Useful analysis should focus on the ioctl precondition: refusing pipe enablement unless the socket is bound to a valid Phonet object. The provided evidence supports a stability/invariant failure; it does not establish privilege escalation, remote reachability, or exploit maturity.

Mitigation direction

  • Update Linux kernels to vendor-supported builds containing the referenced stable fixes.
  • Prioritize systems using or exposing Phonet/PEP functionality.
  • Check distribution advisories for exact package versions and backported fixes.
  • Avoid assuming unaffected status from upstream version strings alone.

Validation and detection

  • Inventory Linux kernel versions across servers, endpoints, appliances, and images.
  • Confirm whether vendor kernels include the referenced stable commits or equivalent backports.
  • Review whether Phonet/PEP kernel support is enabled or used in relevant environments.
  • Track vendor advisory status because the source bundle lacks CVSS and operational mitigations.
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

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CVE-2021-47086 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
LinuxLinuxbdb6e697b2a76c541960b86ab8fda88f3de1adf2, bdb6e697b2a76c541960b86ab8fda88f3de1adf2, bdb6e697b2a76c541960b86ab8fda88f3de1adf2, bdb6e697b2a76c541960b86ab8fda88f3de1adf2, bdb6e697b2a76c541960b86ab8fda88f3de1adf2, bdb6e697b2a76c541960b86ab8fda88f3de1adf2, bdb6e697b2a76c541960b86ab8fda88f3de1adf2, bdb6e697b2a76c541960b86ab8fda88f3de1adf2unaffected
LinuxLinux3.3, 0, 4.4.297, 4.9.295, 4.14.260, 4.19.223, 5.4.169, 5.10.89, 5.15.12, 5.16affected
Weakness

CWE details

No CWE listed

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