CVE Catalog

CVE-2025-38000

HighCVSS 7.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.18%

8th percentile - higher than 8% of all known CVEs

Summary

In the Linux kernel, the HFSC queuing discipline (sch_hfsc) has a queue length accounting bug when enqueuing the first packet to a class. hfsc_enqueue() calls the child's peek() operation before incrementing qlen and backlog, which with qdisc_peek_dequeued() can cause immediate dequeue and drop, leading to inconsistency and potential use-after-free.

Risk Assessment

This vulnerability could lead to inconsistency in HFSC queue management, potentially resulting in system crash or network errors.

Recommendation

Update the Linux kernel to a version containing the fix that moves qlen and backlog increment before the peek() call.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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.

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