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.

An update of the linux package has been released.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-63983)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
333762	Photon OS 5.0: Linux PHSA-2026-5.0-92-0895	Nessus	PhotonOS Local Security Checks	Local	high
328493	Amazon Linux 2023 : bpftool6.12, kernel6.12, kernel6.12-devel (ALAS2023-2026-1968)	Nessus	Amazon Linux Local Security Checks	Local	high
327948	Linux Distros Unpatched Vulnerability : CVE-2026-63983	Nessus	Misc.	Local	medium
322944	Photon OS 5.0: Linux PHSA-2026-5.0-0895	Nessus	PhotonOS Local Security Checks	Local	high

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CVE-2026-63983

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