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Findings

CVE-2025-38000

In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() When enqueuing the first packet…

Published Jun 6, 2025 · updated Oct 15, 2026 · linux linux kernel

In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() When enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the child qdisc's peek() operation before incrementing sch->q.qlen and sch->qstats.backlog. If the child qdisc uses qdisc_peek_dequeued(), this may trigger an immediate dequeue and potential packet drop. In such cases, qdisc_tree_reduce_backlog() is called, but the HFSC qdisc's qlen and backlog have not yet been updated, leading to inconsistent queue accounting. This can leave an empty HFSC class in the active list, causing further consequences like use-after-free. This patch fixes the bug by moving the increment of sch->q.qlen and sch->qstats.backlog before the call to the child qdisc's peek() operation. This ensures that queue length and backlog are always accurate when packet drops or dequeues are triggered during the peek.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 6, 2025 · NIST NVD

    Detected

    In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() When enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the child qdisc's peek() operation before incrementing sch->q.qlen and sch->qstats.backlog. If the child qdisc uses qdisc_peek_dequeued(), this may trigger an immediate dequeue and potential pa

  2. Oct 15, 2026 · NIST NVD

    Updated

    In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() When enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the child qdisc's peek() operation before incrementing sch->q.qlen and sch->qstats.backlog. If the child qdisc uses qdisc_peek_dequeued(), this may trigger an immediate dequeue and potential pa

Affected

  • cpe debian/debian linux11.0
  • cpe linux/linux kernelversion unspecified
  • cpe linux/linux kernel6.15

Sources

  • CVE.orgVulnerability recordCVE-2025-38000

    Official CVE identifier

    cve.org
  • NIST NVDVulnerability recordCVE-2025-38000

    In the Linux kernel, the following vulnerability has been resolved: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() When enqueuing the first packet to an HFSC class, hfsc_enqueue() calls the child qdisc's peek() operation before incrementing sch->q.qlen and

    nvd.nist.gov

References

CVE-2025-38000 · ZeroDay Findings