CVE-2026-98104

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.

Gravité et risque d'exploitation

CVE-2026-98104 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.21 %, ce qui la place devant 9.9 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 7.2.7, 6.18.53, 0, <84223baf21bc9b008444ae9bc38d5fb91fe00b9d, <d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f, <f4ee13ed7f7b22dcd8287fcf477ae37bd84567da, 6.6.158, <=6.6.*, 6.1.189, 7801db8aec957fa6610efe0ee26a6c8bc0f1d73b, <=6.18.*, 7.3, <=7.2.*, <=*, 3.16, <3.16, <feab9261b537df4ebb8350e4779bc185373059fd, 6.12.111, <f594f04268d01c5fdc975f3f51fc219ea2159ac6, <6890e28840bae4f6805e8de981c4ec8e12a4e064) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/f4ee13ed7f7b22dcd8287fcf477ae37bd84567da
• https://git.kernel.org/stable/c/84223baf21bc9b008444ae9bc38d5fb91fe00b9d
• https://git.kernel.org/stable/c/6890e28840bae4f6805e8de981c4ec8e12a4e064
• https://git.kernel.org/stable/c/feab9261b537df4ebb8350e4779bc185373059fd
• https://git.kernel.org/stable/c/f594f04268d01c5fdc975f3f51fc219ea2159ac6
• https://git.kernel.org/stable/c/d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f