In the Linux kernel, the following vulnerability has been resolved: net/sched: fix packet loop on netem when duplicate is on When netem duplicates a… (CVE-2026-63983)
A vulnerability in the Linux kernel's netem packet scheduler could cause a packet duplication loop, leading to stack or memory exhaustion. This occurs when netem duplicates a packet and re-enqueues it, potentially causing recursive duplication if multiple netem qdiscs are in the queueing discipline tree. The issue arises from unsafe shared state handling without proper locking. The fix involves marking packets with a depth field to prevent repeated duplication regardless of tree topology or concurrency.
AI Analysis
Technical Summary
The Linux kernel vulnerability CVE-2026-63983 involves the netem packet scheduler duplicating packets recursively when multiple netem qdiscs are present. The original duplication guard used a per-qdisc shared state that was unsafe under concurrent enqueue operations, allowing packets to be duplicated repeatedly until stack or memory exhaustion occurs. The fix replaces this mechanism by using the skb tc_depth field to track duplication depth per packet, incrementing it before re-enqueue and skipping duplication if already non-zero. This approach safely prevents recursive duplication regardless of queueing discipline tree structure or concurrency.
Potential Impact
This vulnerability can lead to resource exhaustion (stack or memory) on affected Linux systems due to recursive packet duplication in the netem scheduler. This could potentially cause denial of service conditions by exhausting system resources handling network traffic.
Mitigation Recommendations
A fix for this vulnerability has been implemented in the Linux kernel by changing the duplication guard mechanism to use per-packet state (skb tc_depth) instead of shared qdisc state. Users should apply the official Linux kernel updates that include this fix. Patch status is not explicitly confirmed in the provided data; check the vendor or Linux kernel advisories for the exact fixed versions and update accordingly.
In the Linux kernel, the following vulnerability has been resolved: net/sched: fix packet loop on netem when duplicate is on When netem duplicates a… (CVE-2026-63983)
Description
A vulnerability in the Linux kernel's netem packet scheduler could cause a packet duplication loop, leading to stack or memory exhaustion. This occurs when netem duplicates a packet and re-enqueues it, potentially causing recursive duplication if multiple netem qdiscs are in the queueing discipline tree. The issue arises from unsafe shared state handling without proper locking. The fix involves marking packets with a depth field to prevent repeated duplication regardless of tree topology or concurrency.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel vulnerability CVE-2026-63983 involves the netem packet scheduler duplicating packets recursively when multiple netem qdiscs are present. The original duplication guard used a per-qdisc shared state that was unsafe under concurrent enqueue operations, allowing packets to be duplicated repeatedly until stack or memory exhaustion occurs. The fix replaces this mechanism by using the skb tc_depth field to track duplication depth per packet, incrementing it before re-enqueue and skipping duplication if already non-zero. This approach safely prevents recursive duplication regardless of queueing discipline tree structure or concurrency.
Potential Impact
This vulnerability can lead to resource exhaustion (stack or memory) on affected Linux systems due to recursive packet duplication in the netem scheduler. This could potentially cause denial of service conditions by exhausting system resources handling network traffic.
Mitigation Recommendations
A fix for this vulnerability has been implemented in the Linux kernel by changing the duplication guard mechanism to use per-packet state (skb tc_depth) instead of shared qdisc state. Users should apply the official Linux kernel updates that include this fix. Patch status is not explicitly confirmed in the provided data; check the vendor or Linux kernel advisories for the exact fixed versions and update accordingly.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-rj36-qxvm-r8rm
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-63983"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- null
Threat ID: 6a5d27aa2a4a8d598912dbcc
Added to database: 07/19/2026, 19:38:18 UTC
Last enriched: 07/19/2026, 20:00:36 UTC
Last updated: 07/20/2026, 17:44:00 UTC
Views: 11
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