CVE-2026-63983

Service interruption via recursive netem packet duplication

Published Jul 19, 2026 · Updated Jul 19, 2026

Denial of service in affected Linux Kernel releases allows attackers to exhaust stack or memory through nested netem qdiscs. In sch_netem.c, a duplicated packet is re-enqueued at the root qdisc and can be duplicated again by another netem because the shared q->duplicate guard does not cover the full enqueue path. Reachability requires a qdisc tree with netem duplication enabled; recursion continues until kernel stack or memory is exhausted, interrupting service.

CVSS severityUnavailable
Unscored
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Linux Kernel releases allows attackers to exhaust stack or memory through nested netem qdiscs. In sch_netem.c, a duplicated packet is re-enqueued at the root qdisc and can be duplicated again by another netem because the shared q->duplicate guard does not cover the full enqueue path. Reachability requires a qdisc tree with netem duplication enabled; recursion continues until kernel stack or memory is exhausted, interrupting service.

The record

CVE
CVE-2026-63983
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0afb51e72855971dba83b3c6b70c547c2d1161fd <1a298a514ce766c6d0c232991a390fec67af81ad
  2. Affected versionversion=0afb51e72855971dba83b3c6b70c547c2d1161fd <9552b11e3edabc97cfcd9f29103d5afbce7ae183
  3. Affected versionversion=0afb51e72855971dba83b3c6b70c547c2d1161fd <cfb2616042767ab31260d4f39190c381bec8b12e
  4. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linux Kernelversion=0afb51e72855971dba83b3c6b70c547c2d1161fd <1a298a514ce766c6d0c232991a390fec67af81ad; version=0afb51e72855971dba83b3c6b70c547c2d1161fd <9552b11e3edabc97cfcd9f29103d5afbce7ae183; version=0afb51e72855971dba83b3c6b70c547c2d1161fd <cfb2616042767ab31260d4f39190c381bec8b12e; version=2.6.12

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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