CVE-2026-89544
Vulnérabilité élevée dans Linux (Linux)
Description
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: fix gssx_dec_option_array error path bugs Four coupled defects in the gssx XDR option-array decoder make the error paths unsafe: a NULL deref in the caller, a refcount leak on the decoded group_info, and a latent use-after-free that the leak fix would otherwise expose. gssx_dec_option_array() sets oa->count = 1 before allocating oa->data. If that allocation fails, -ENOMEM is returned with oa->count == 1 and oa->data == NULL. All other error paths jump to free_oa: which frees oa->data and NULLs it but also leaves oa->count == 1. The caller trusts the count: gssp_accept_sec_context_upcall() gssx_dec_accept_sec_context() gssx_dec_option_array() /* fails, count=1 data=NULL */ data = res.options.data[0].value /* NULL deref */ Independently, free_creds: releases the partially decoded svc_cred with a bare kfree(creds). gssx_dec_linux_creds() installs a groups_alloc() result into creds->cr_group_info; that object is kvmalloc-backed and refcounted, and only put_group_info() reaches kvfree(). A plain kfree(creds) drops the wrapper and leaks the group_info allocation. The natural fix for the leak is to call free_svc_cred(creds) before kfree(creds), but free_svc_cred() invokes put_group_info() on creds->cr_group_info unconditionally when non-NULL. The existing out_free_groups: path in gssx_dec_linux_creds() already called groups_free() on that pointer without clearing it, so once free_svc_cred() is wired in, the subsequent put_group_info() would touch freed memory. Fix all four together: - Move the oa->count = 1 assignment below the oa->data allocation so it is never set when oa->data is NULL. - Reset oa->count to 0 at free_oa: so count and data stay coherent and the caller sees an empty option array. - Call free_svc_cred(creds) before kfree(creds) at free_creds: so the refcounted cr_group_info is released. free_svc_cred() either NULL-guards each field explicitly (cr_group_info has an if() check) or delegates to a helper that is NULL-safe itself (kfree for the string fields, gss_mech_put() which guards with if(gm) at gss_mech_switch.c:342), so it is safe to call on a partially decoded svc_cred where only cr_uid/cr_gid/cr_group_info have been written and everything else is zero from kzalloc. - In gssx_dec_linux_creds()'s out_free_groups: path, release cr_group_info with put_group_info() rather than groups_free() so the teardown matches free_svc_cred()'s refcount-aware path, and clear the pointer so a later free_svc_cred() on the same creds does not release it a second time.
Gravité et risque d'exploitation
CVE-2026-89544 obtient un score CVSS de 7.5/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.59 %, ce qui la place devant 47.3 % des CVE référencées.
Que faire ?
- Vérifiez si Linux (versions 6.9, <5.11, <=6.12.*, <5e9a94539b1ec17a89177d952badfd0d844d694a, 5e6013ae2c8d420faea553d363935f65badd32c3, 0, 7.2.4, 4.19.311, 6.1.83, 6.7.11, 3cfcfc102a5e57b021b786a755a38935e357797d, 5.15.153, 6.18.51, 9806c2393cd2ab0a8e7bb9ffae02ce20e3112ec4, <6.8, <4.20, <f85a83774d7f4e2ac71c0c384df0dfb6f7d0179a, 6.8.2, 5.4.273, bfa9d86d39a0fe4685f90c3529aa9bd62a9d97a8, bb336cd8d5ecb69c430ebe3e7bcff68471d93fa8, <5.5, <5.16, <=6.18.*, <6.2, <fb30241f7ccace372ee83017891549f23a715581, 934212a623cbab851848b6de377eb476718c3e4c, <=7.2.*, b97c37978ca825557d331c9012e0c1ddc0e42364, dd292e884c649f9b1c18af0ec75ca90b390cd044, 6.6.23, <6.7, 5.10.214, <3ff45361e9469e85c0f86b8e7b82c63e50bab8ef, <=*, <6.9, 6.12.111, 996997d1fb2126feda550d6adcedcbd94911fc69, 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.