CVE Catalog

CVE-2026-63983

Low risk· EPSS 6%
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.17%

6th percentile - higher than 6% of all known CVEs

Summary

A vulnerability was found in the Linux kernel's netem packet duplication mechanism. When netem duplicates a packet, it re-enqueues the copy at the root qdisc, which can cause an infinite duplication loop if another netem is present in the tree. The fix uses the tc_depth field in the skb structure to prevent multiple duplications of the same packet.

Risk Assessment

An attacker could exploit this vulnerability to exhaust system stack or memory, leading to a denial of service (DoS) and potential system crash.

Recommendation

Immediately update the Linux kernel to a version containing the fix (commit addressing the issue).

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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 packet it re-enqueues the copy at the root qdisc. If another netem sits in the tree the copy can be duplicated again, recursing until the stack or memory is exhausted. The original duplication guard temporarily zeroed q->duplicate around the re-enqueue, but that does not cover all cases because it is per-qdisc state shared across all concurrent enqueue paths and is not safe without additional locking. Use the skb tc_depth field introduced in an earlier patch: - increment it on the duplicate before re-enqueue - skip duplication for any skb whose tc_depth is already non-zero. This marks the packet itself rather than mutating qdisc state, therefore it is safe regardless of tree topology or concurrency.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS