CVE-2026-89540

Description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: init gssp_lock before publishing proc entry create_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy via proc_create_data() before init_gssp_clnt() runs mutex_init() on sn->gssp_lock. Once the dentry is linked under proc_subdir_lock it is immediately reachable from userspace, so a write that lands in the window drives set_gssp_clnt() into mutex_lock() on a zero-initialized struct mutex. create_use_gss_proxy_proc_entry(net) proc_create_data("use-gss-proxy", ...) /* dentry live */ init_gssp_clnt(sn) mutex_init(&sn->gssp_lock) /* too late */ write_gssp() set_gssp_clnt(net) mutex_lock(&sn->gssp_lock) /* uninitialized */ gssp_rpc_create(...) sn->gssp_clnt = clnt mutex_unlock(&sn->gssp_lock) The window spans only the two statements between proc_create_data() returning and init_gssp_clnt(), so a writer reaches it only if the registering thread is preempted there while another task is already opening the freshly published file. register_pernet_subsys() runs in preemptible context under pernet_ops_rwsem, so that preemption is possible, and the window widens on auth_rpcgss module load, when the proc entry is created for every live net namespace whose tasks are already running. A writer that wins the race locks a zero-filled struct mutex. On CONFIG_DEBUG_MUTEXES the missing magic value trips a "lock used without init" splat; on a production kernel the fast path acquires the lock via CMPXCHG(owner, 0, current). In the latter case a second writer that arrives before init_gssp_clnt() re-zeroes owner can enter set_gssp_clnt() concurrently, shut down the first writer's clnt while it is still in use, and leak the loser's clnt. Fix by initializing sn->gssp_lock in sunrpc_init_net() so its lifetime matches the sunrpc_net it lives in. sn->gssp_clnt is already NULL from the kzalloc that backs net_generic storage, so the lazy helper is no longer needed; drop init_gssp_clnt(), its prototype, and the call from create_use_gss_proxy_proc_entry(). sunrpc.ko is a build-time dependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on every netns before any auth_gss pernet init can publish the proc entry.

Gravité et risque d'exploitation

CVE-2026-89540 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.13 %, ce qui la place devant 2.3 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <5ce1ed6159731a41fdd0b03eedbed4e147036a5a, <=6.1.*, <=6.12.*, 030d794bf49855f5e2a9e8dfbfad34211d1eb08b, 5.15.221, 5.10.270, <7f5bcdc8da15077ebe846c2756a5a17741021410, 0, 7.2.4, <edeefb111d6181a4aa278f415b005efe284b9489, <3f019571928b269feebcff59926ec13294215e0e, 6.1.188, <b3526ae3351968f6726bcbe25d8d09973ad79109, <3.10, <=5.10.*, <=6.6.*, 6.6.157, <159a4fab7170badd6c4a553aef81cac079d6f4ee, <89c8e0733e8c46b7973503f15b1b31a8587d8030, <=6.18.*, <=7.2.*, <f15b87521168c2a92cb1931f532cba422f856f01, <=*, <=5.15.*, 3.10, 6.18.50, 6.12.109, 7.3) 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/159a4fab7170badd6c4a553aef81cac079d6f4ee
• https://git.kernel.org/stable/c/b3526ae3351968f6726bcbe25d8d09973ad79109
• https://git.kernel.org/stable/c/7f5bcdc8da15077ebe846c2756a5a17741021410
• https://git.kernel.org/stable/c/89c8e0733e8c46b7973503f15b1b31a8587d8030
• https://git.kernel.org/stable/c/f15b87521168c2a92cb1931f532cba422f856f01
• https://git.kernel.org/stable/c/edeefb111d6181a4aa278f415b005efe284b9489
• https://git.kernel.org/stable/c/3f019571928b269feebcff59926ec13294215e0e
• https://git.kernel.org/stable/c/5ce1ed6159731a41fdd0b03eedbed4e147036a5a