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CVE-2025-21702 is a Linux kernel traffic-control vulnerability in pfifo_tail_enqueue(), used by the pfifo_head_drop queueing discipline. When an empty child queue has sch->limit set to zero, the function attempts to drop a nonexistent packet, then incorrectly enqueues the incoming packet and increments the child queue length while returning NET_XMIT_CN. A parent queueing discipline such as HFSC or DRR can consequently leave its own queue length unchanged. This violates the invariant that a parent's queue length equals the sum of its children's queue lengths and can enable user-to-kernel privilege escalation when the vulnerable code path is reachable.
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12 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel packet-scheduling flaw in pfifo_tail_enqueue() allows a zero-limit child queue to accept a packet without updating its parent queue's packet count consistently. This queue-length inconsistency can enable local user-to-kernel privilege escalation when the vulnerable code is reachable. The advisory assigns a CVSS v3 base score of 7.0 and identifies a fixed package version of 18613.164.93.
A Linux kernel packet-scheduler flaw allows pfifo_tail_enqueue() to enqueue a packet despite a zero queue limit while returning NET_XMIT_CN. This can create inconsistent queue lengths between parent and child queueing disciplines, potentially enabling local user-to-kernel privilege escalation when the vulnerable path is reachable. The reference assigns a CVSS v3 base score of 7.0, with low privileges required and high attack complexity.
Linux kernel packet-scheduler handling flaw when queue limit is zero.
A Linux kernel traffic-control queuing discipline (qdisc) accounting flaw in pfifo_tail_enqueue. Under a zero queue limit, it can create inconsistent parent/child queue lengths, potentially enabling local user-to-kernel privilege escalation.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
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