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CVE Record

CVE-2021-46998: ethernet:enic: Fix a use after free bug in enic_hard_start_xmit

In the Linux kernel, the following vulnerability has been resolved: ethernet:enic: Fix a use after free bug in enic_hard_start_xmit In enic_hard_start_xmit, it calls enic_queue_wq_skb(). Inside enic_queue_wq_skb, if some error happens, the skb will be freed by dev_kfree_skb(skb). But the freed skb is still used in skb_tx_timestamp(skb). My patch makes enic_queue_wq_skb() return error and goto spin_unlock() incase of error. The solution is provided by Govind. See https://lkml.org/lkml/2021/4/30/961.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-46998 is a Linux kernel bug in the enic Ethernet driver. During packet transmission, an error path can free a network buffer and then continue using it. The sources show a kernel fix, but do not provide CVSS, impact scope, or evidence of exploitation.

Executive priority

Handle through the next kernel maintenance cycle, with higher priority for production systems using enic-backed network interfaces. Escalate if a vendor advisory later assigns high severity or reports exploitation.

Technical view

The issue is a use-after-free in enic_hard_start_xmit. enic_queue_wq_skb can free skb on error via dev_kfree_skb, after which skb_tx_timestamp may still reference the freed skb. The fix changes error handling so execution exits before the freed skb is reused.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions with the enic Ethernet driver path in use. The bundle identifies Linux as affected and lists kernel versions and stable commits, but does not name distributions, configurations, or required hardware conditions.

Exploitation context

The provided sources do not report active exploitation, and KEV is false. They also do not describe attacker prerequisites, reachability, or practical exploitability. Treat this as a kernel memory-safety defect requiring patch verification rather than an emergency exploitation event.

Researcher notes

Evidence is limited to the CVE description and Linux stable references. No CWE, CVSS vector, attacker model, exploit status, or distribution-specific fixed versions are provided in the bundle. Avoid broad exposure claims without confirming enic driver use.

Mitigation direction

  • Apply a Linux kernel update containing the referenced stable fix or distro backport.
  • Prioritize systems using the enic Ethernet driver or Cisco virtual interface hardware.
  • Check distribution advisories for exact fixed package versions.
  • Reboot or otherwise load the fixed kernel after updating.
  • Monitor vendor guidance for any later severity or workaround details.

Validation and detection

  • Inventory Linux kernel versions across managed hosts.
  • Identify hosts where the enic driver is present or loaded.
  • Confirm the fixed kernel package or referenced commit is installed.
  • Verify systems booted into the updated kernel after patching.
  • Run network regression checks for affected NICs after update.
Prepared
Confidence
medium
Sources
8

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-2021-46998 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
7Source 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

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxfb7516d42478ebc8e2f00efb76ef96f7b68fd8d3, fb7516d42478ebc8e2f00efb76ef96f7b68fd8d3, fb7516d42478ebc8e2f00efb76ef96f7b68fd8d3, fb7516d42478ebc8e2f00efb76ef96f7b68fd8d3, fb7516d42478ebc8e2f00efb76ef96f7b68fd8d3, fb7516d42478ebc8e2f00efb76ef96f7b68fd8d3unaffected
LinuxLinux4.16, 0, 4.19.191, 5.4.120, 5.10.38, 5.11.22, 5.12.5, 5.13affected
Weakness

CWE details

No CWE listed

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