CVE-2026-63983
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.
Affected versions
Linux kernel versions
2.6.12
and later are affected. Fixed in
6.12.93,
7.0.12,
7.1
and their respective stable series.
References
3 totalFrequently asked questions
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What is CVE-2026-63983?
CVE-2026-63983 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 2.6.12 onward and has been patched in 6.12.93, 7.0.12 and 7.1. CVE-2026-63983 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-63983?
Yes — CVE-2026-63983 has been patched. Fixed versions include 6.12.93, 7.0.12 and 7.1. If you are running Linux kernel 2.6.12 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-63983 actively exploited?
No — CVE-2026-63983 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.