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CVE Record

CVE-2022-48976: netfilter: flowtable_offload: fix using __this_cpu_add in preemptible

In the Linux kernel, the following vulnerability has been resolved: netfilter: flowtable_offload: fix using __this_cpu_add in preemptible flow_offload_queue_work() can be called in workqueue without bh disabled, like the call trace showed in my act_ct testing, calling NF_FLOW_TABLE_STAT_INC() there would cause a call trace: BUG: using __this_cpu_add() in preemptible [00000000] code: kworker/u4:0/138560 caller is flow_offload_queue_work+0xec/0x1b0 [nf_flow_table] Workqueue: act_ct_workqueue tcf_ct_flow_table_cleanup_work [act_ct] Call Trace: <TASK> dump_stack_lvl+0x33/0x46 check_preemption_disabled+0xc3/0xf0 flow_offload_queue_work+0xec/0x1b0 [nf_flow_table] nf_flow_table_iterate+0x138/0x170 [nf_flow_table] nf_flow_table_free+0x140/0x1a0 [nf_flow_table] tcf_ct_flow_table_cleanup_work+0x2f/0x2b0 [act_ct] process_one_work+0x6a3/0x1030 worker_thread+0x8a/0xdf0 This patch fixes it by using NF_FLOW_TABLE_STAT_INC_ATOMIC() instead in flow_offload_queue_work(). Note that for FLOW_CLS_REPLACE branch in flow_offload_queue_work(), it may not be called in preemptible path, but it's good to use NF_FLOW_TABLE_STAT_INC_ATOMIC() for all cases in flow_offload_queue_work().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2022-48976 is a Linux kernel netfilter flowtable bug that can trigger a kernel call trace when a statistic counter is updated in a preemptible workqueue path. The public record shows it has been fixed upstream, but does not provide CVSS, CWE, or confirmed real-world impact.

Executive priority

Track this as a kernel maintenance item until vendor advisories identify business-critical exposure. There is no cited evidence of active exploitation, but affected network and security infrastructure should receive normal kernel patch priority.

Technical view

The issue is in nf_flow_table flow_offload_queue_work(). It used NF_FLOW_TABLE_STAT_INC(), which can call __this_cpu_add() while preemption is possible. The fix changes this path to NF_FLOW_TABLE_STAT_INC_ATOMIC(), avoiding the preemption warning seen during act_ct flow table cleanup work.

Likely exposure

Exposure is most relevant to Linux systems running affected kernel builds that include netfilter flowtable offload and related act_ct paths. The source bundle names Linux kernel versions and stable commits, but distro package mappings require vendor advisory confirmation.

Exploitation context

The source bundle does not show CISA KEV listing, public exploitation, exploit code, or attacker prerequisites. Evidence is limited to a kernel call trace observed during testing and upstream stable fixes.

Researcher notes

Do not infer remote code execution, privilege escalation, or denial-of-service impact from the provided record alone. The evidence supports a correctness bug in a preemptible context, fixed by using the atomic statistic increment helper.

Mitigation direction

  • Update to a vendor kernel containing the referenced stable fixes.
  • Check Linux distribution advisories for exact fixed package versions.
  • Prioritize systems using netfilter flowtable offload or traffic control conntrack paths.
  • If patching is delayed, ask the vendor for supported configuration mitigations.

Validation and detection

  • Inventory Linux kernel versions across exposed servers and appliances.
  • Confirm whether nf_flow_table and act_ct-related functionality is used.
  • Compare running kernels against vendor fixed package guidance.
  • Review kernel logs for the referenced __this_cpu_add preemptible call trace.
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

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CVE-2022-48976 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
1ADP providers
3Source 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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxb038177636f83bbf87c2b238706474145dd2cd04, b038177636f83bbf87c2b238706474145dd2cd04, 5345d78ae64d5a760c211cd2da995dc71c5b29e4unaffected
LinuxLinux6.0, 0, 6.0.13, 6.1affected
Weakness

CWE details

No CWE listed

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