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CVE-2026-31669

Vulnérabilité critique dans Linux (Linux)

CVSS 9.8 · Critique
EPSS 0.8%
Linux•Linux•Versions : <eb9c6aeb512f877cf397deb1e4526f646c70e4a7, <=6.1.*, <=6.12.*, 6.18.23, 0, 7.0, <15fa9ead4d5e6b6b9c794e84144146c917f2cb62, 5.12, <=6.6.*, <b313e9037d98c13938740e5ebda7852929366dff, <=6.19.*, 6.1.169, 5.15.203, <fb1f54b7d16f393b8b65d328410f78b4beea8fcc, b19bc2945b40b9fd38e835700907ffe8534ef0de, <=6.18.*, <3fd6547f5b8ac99687be6d937a0321efda760597, <5.12, 6.6.135, 6.19.13, <=*, <=5.15.*, 6.12.82, <f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47, <9b55b253907e7431210483519c5ad711a37dafa1

Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: fix slab-use-after-free in __inet_lookup_established The ehash table lookups are lockless and rely on SLAB_TYPESAFE_BY_RCU to guarantee socket memory stability during RCU read-side critical sections. Both tcp_prot and tcpv6_prot have their slab caches created with this flag via proto_register(). However, MPTCP's mptcp_subflow_init() copies tcpv6_prot into tcpv6_prot_override during inet_init() (fs_initcall, level 5), before inet6_init() (module_init/device_initcall, level 6) has called proto_register(&tcpv6_prot). At that point, tcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab remains NULL permanently. This causes MPTCP v6 subflow child sockets to be allocated via kmalloc (falling into kmalloc-4k) instead of the TCPv6 slab cache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so when these sockets are freed without SOCK_RCU_FREE (which is cleared for child sockets by design), the memory can be immediately reused. Concurrent ehash lookups under rcu_read_lock can then access freed memory, triggering a slab-use-after-free in __inet_lookup_established. Fix this by splitting the IPv6-specific initialization out of mptcp_subflow_init() into a new mptcp_subflow_v6_init(), called from mptcp_proto_v6_init() before protocol registration. This ensures tcpv6_prot_override.slab correctly inherits the SLAB_TYPESAFE_BY_RCU slab cache.

Gravité et risque d'exploitation

CVE-2026-31669 obtient un score CVSS de 9.8/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.84 %, ce qui la place devant 57.3 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <eb9c6aeb512f877cf397deb1e4526f646c70e4a7, <=6.1.*, <=6.12.*, 6.18.23, 0, 7.0, <15fa9ead4d5e6b6b9c794e84144146c917f2cb62, 5.12, <=6.6.*, <b313e9037d98c13938740e5ebda7852929366dff, <=6.19.*, 6.1.169, 5.15.203, <fb1f54b7d16f393b8b65d328410f78b4beea8fcc, b19bc2945b40b9fd38e835700907ffe8534ef0de, <=6.18.*, <3fd6547f5b8ac99687be6d937a0321efda760597, <5.12, 6.6.135, 6.19.13, <=*, <=5.15.*, 6.12.82, <f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47, <9b55b253907e7431210483519c5ad711a37dafa1) 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

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