LiveActive security incident?Get immediate response
CVE Record

CVE-2021-47312: netfilter: nf_tables: Fix dereference of null pointer flow

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: Fix dereference of null pointer flow In the case where chain->flags & NFT_CHAIN_HW_OFFLOAD is false then nft_flow_rule_create is not called and flow is NULL. The subsequent error handling execution via label err_destroy_flow_rule will lead to a null pointer dereference on flow when calling nft_flow_rule_destroy. Since the error path to err_destroy_flow_rule has to cater for null and non-null flows, only call nft_flow_rule_destroy if flow is non-null to fix this issue. Addresses-Coverity: ("Explicity null dereference")

MediumCVSS 5.5Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel flaw can crash an affected system through a null pointer dereference in nf_tables error handling. The business impact is availability, not data theft or tampering. It requires local low-privileged access, so internet-facing remote exposure is not indicated by the supplied sources.

Executive priority

Treat this as a routine but real availability risk. It is not evidenced as remotely exploitable or actively exploited, but kernel crashes can disrupt important systems. Patch through normal Linux maintenance, faster for shared or multi-user hosts.

Technical view

CVE-2021-47312 is a CWE-476 null pointer dereference in Linux netfilter nf_tables. If hardware offload is not set, flow remains NULL, but an error path can still call nft_flow_rule_destroy on it. The upstream stable fix only destroys the flow object when it is non-null.

Likely exposure

Exposure is most relevant on Linux systems running affected kernel code where local authenticated users can exercise relevant nf_tables paths. The supplied bundle does not provide a clear affected version range beyond kernel commit references and Linux 5.13.2 context.

Exploitation context

The CVSS vector is local, low complexity, low privileges, no user interaction, with high availability impact. The source bundle marks CISA KEV as false and provides no cited evidence of active exploitation or public exploit availability.

Researcher notes

Evidence supports a kernel availability flaw fixed by adding a non-null guard before destroying flow state. The bundle does not establish affected distribution package ranges, exploitation in the wild, or compensating controls specific to nf_tables.

Mitigation direction

  • Apply a kernel update containing the referenced stable nf_tables fix.
  • Check your Linux distribution advisory for exact affected and fixed package versions.
  • Prioritize multi-user systems and hosts granting local shell access.
  • Reduce unnecessary local account access until kernel patching is complete.

Validation and detection

  • Inventory Linux kernel versions across servers, workstations, and appliances.
  • Confirm vendor packages include the referenced stable commit or equivalent backport.
  • Review vulnerability scanner findings against distro-specific fixed versions.
  • Validate patch rollout with standard uptime and netfilter regression checks.
Prepared
Confidence
medium
Sources
4

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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-476: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2021-47312 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

1CVSS vectors
3Timeline events
2ADP providers
3Source links

SSVC decision data

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

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2021-47312Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux09b1f676e2e0bbff67c568672c565c6f31470157, 3c5e44622011b9ea21bd425875dcccfc9a158f5funaffected
LinuxLinux5.13.2unaffected
Weakness

CWE details

CWE-476

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

CWE-476 · source CWE mapping

NULL Pointer Dereference

NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs