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CVE-2026-98104— net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： net/sched: cls_u32：修复节点 ID 池耗尽时产生的重复句柄（handle）问题 当 的两个分配范围均已满时， 会回退并返回最大值（ ），而不是报告错误。 盲目信任该返回值，并插入一个新的 ，其句柄（handle）在哈希表中已处于活跃状态，从而破坏了表内节点 ID 空间中句柄的唯一性。 该句柄从未在 中预留，因此后续所有执行 的错误路径都会移除另一个活跃 的预留，随后该句柄会被重复使用——一次添加失败会导致更多的重复句柄。 该 4095 的限制是针对每个

AI Predicted 7.8 Difficulty: Easy EPSS 0.21% · P10

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux 7801db8aec957fa6610efe0ee26a6c8bc0f1d73b< f4ee13ed7f7b22dcd8287fcf477ae37bd84567da affected
7801db8aec957fa6610efe0ee26a6c8bc0f1d73b< 84223baf21bc9b008444ae9bc38d5fb91fe00b9d affected
7801db8aec957fa6610efe0ee26a6c8bc0f1d73b< 6890e28840bae4f6805e8de981c4ec8e12a4e064 affected
7801db8aec957fa6610efe0ee26a6c8bc0f1d73b< feab9261b537df4ebb8350e4779bc185373059fd affected
7801db8aec957fa6610efe0ee26a6c8bc0f1d73b< f594f04268d01c5fdc975f3f51fc219ea2159ac6 affected
7801db8aec957fa6610efe0ee26a6c8bc0f1d73b< d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f affected
3.16 affected
< 3.16 unaffected
… +6 more rows
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I. Basic Information for CVE-2026-98104

Vulnerability Information
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Vulnerability Title
net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted gen_new_kid() falls back to returning max (htid | 0xFFF) when both idr_alloc_u32() ranges are full, instead of reporting an error. u32_change() trusts that value and inserts a new knode with a handle that is already live in the hash table, breaking handle uniqueness within the table's node ID space. The handle was never reserved in ht->handle_idr, so every later error path that does idr_remove(&ht->handle_idr, handle) removes the reservation of a different, live knode, which is then reused — one failed add compounds into further duplicates. The 4095 limit is per (table, bucket) — ht->handle_idr is per hash table and the range is derived from htid (bucketid), so a table with divisor 256 can legitimately hold 256*4095 knodes. The sibling helper gen_new_htid() has the same silent in-band failure: it returns 0 when the tp_c handle pool (1..0x7FF) is full, and u32_init() publishes the root hash table with handle 0 without checking. Two root tables with handle 0 alias in u32_lookup_ht(), allowing cross-tcf_proto knode add/lookup/delete. Add the same exhaustion check that the divisor path already has. Return an error so u32_change() fails with ENOSPC/ENOMEM when the node ID space is exhausted, and so u32_init() fails with -ENOMEM when the hash table ID space is exhausted. The extack message distinguishes pool exhaustion (-ENOSPC) from a transient allocation failure (-ENOMEM). Conditions to recreate the bug: - CONFIG_NET_SCHED=y, CONFIG_CLS_U32=y (or =m with module loaded) - Create a clsact qdisc on a device, then add 4095 u32 filters with auto-generated handles to fill the node ID space for the root hash table (single bucket). The 4096th auto-handle filter add triggers the duplicate handle (fh 800::fff reused). Reachable at Level 2 (unshare -Urn, namespace-local CAP_NET_ADMIN). - For gen_new_htid: create 2047 u32 proto entries on the same block to fill the tp_c handle pool, then create one more. The root table gets handle 0 and aliases with other handle-0 root tables.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 7801db8aec957fa6610efe0ee26a6c8bc0f1d73b ~ f4ee13ed7f7b22dcd8287fcf477ae37bd84567da -
Linux Linux 3.16 -

II. Public POCs for CVE-2026-98104

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III. Intelligence Information for CVE-2026-98104

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Patches & Fixes for CVE-2026-98104 (6)

Same Patch Batch · Linux · 2026-09-25 · 372 CVEs total

CVE-2026-100075 9.8 CRITICAL RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters
CVE-2026-97555 8.8 HIGH smb: client: fix heap overflow in DACL owner/group rewrite
CVE-2026-97957 8.8 HIGH net: hinic: fix mailbox segment buffer overflow
CVE-2026-97527 8.8 HIGH scsi: qla2xxx: Serialize NVMe unsol ctx list with a per-fcport lock
CVE-2026-97528 8.8 HIGH scsi: qla2xxx: Unlink NVMe unsol ctx before freeing on LS reject error
CVE-2026-98115 8.8 HIGH ksmbd: safely drain sessions during logoff
CVE-2026-97525 8.2 HIGH x86/mm/pat: Allocate split page tables as kernel page tables
CVE-2026-98069 8.1 HIGH net/rds: acquire the fastpath locks in rds_conn_shutdown()
CVE-2026-97573 8.1 HIGH bnxt_en: Handle buffer allocation failure in bnxt_rx_ring_reset()
CVE-2026-97570 8.1 HIGH bnxt_en: Bound SW TPA IDs to prevent crashes
CVE-2026-98130 8.1 HIGH sctp: fix a TOCTOU race in SCTP_CMD_TIMER_START
CVE-2026-98070 8.1 HIGH net/rds: acquire RDS_IN_XMIT in rds_tcp_reset_callbacks()
CVE-2026-98002 7.8 HIGH iommu/amd: Fix ineffective error check in nested domain allocation
CVE-2026-97575 7.8 HIGH media: v4l2-ctrls: validate AV1 tile counts
CVE-2026-97576 7.8 HIGH media: v4l2-ctrls: validate HEVC tile counts
CVE-2026-97941 7.8 HIGH mm/slab: take n->list_lock in __slab_try_return_freelist() to avoid race
CVE-2026-98112 7.8 HIGH ksmbd: fix listener task lifetime on netdev events
CVE-2026-97937 7.8 HIGH ftrace: fork: Initialize function graph state before copy_exec_state()
CVE-2026-97580 7.8 HIGH media: rkvdec: bound HEVC tile loops and PPS id to the array capacity
CVE-2026-97940 7.8 HIGH ipv6: fix fib6 walker UAF on seq stop

Showing top 20 of 372 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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