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CVE-2026-89696

Vulnérabilité élevée dans Linux (Linux)

CVSS 7.5 · Élevée
EPSS 0.8%
Linux•Linux•Versions : <=6.1.*, <=6.12.*, 5.15.221, <bf4d338dc8625d70c7f2cb0657d66851a7ac9154, 5.10.270, 0, 7.2.4, 6.1.188, 5.6, <=5.10.*, <=6.6.*, 6.6.157, b9e8638e3d9ed8334f1f7071e081860aac37e83e, <311f7d926630940650447cbd1c932b076b40a6c4, <00c84f4eec715e501efc080a5670114189e42507, <=6.18.*, <977e6f006a7a3ffc4216ae6034f768f8de6fd138, 7.3, <=7.2.*, <2d9846fd1c767920fddd4bde30eb35cd2969df13, <5.6, <=*, <35f248bd40b47b229d4999581df45b97daadd977, <=5.15.*, 6.18.50, 6.12.109, <ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32, <c59738a00aa51b16adc1b5ceb7c80877168efb4d

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref When CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can return success with fh_dentry and fh_export both NULL if fh_verify() returns nfserr_stale and putfh->no_verify is true. The NFSD4_FH_FOREIGN flag is set, but the compound dispatch loop only uses this flag to bypass the nfserr_nofilehandle check -- it does not prevent subsequent ops from running with a NULL fh_dentry. A remote client can exploit this by crafting a COMPOUND that includes an inter-SSC COPY (which causes check_if_stalefh_allowed() to set no_verify=true on the saved PUTFH) with an additional op inserted between the source PUTFH and SAVEFH. For example, SETATTR calls fh_want_write() which dereferences fh_export->ex_path.mnt without calling fh_verify() first, causing a NULL pointer dereference in the nfsd kthread. Fix this by gating the dispatch loop: when NFSD4_FH_FOREIGN is set and fh_dentry is NULL, only OP_SAVEFH (needed for the inter-SSC flow) and ops with ALLOWED_WITHOUT_FH (which don't need a resolved filehandle) may proceed. All other ops receive nfserr_stale, per RFC 7862 Section 15.2.3 which specifies that foreign filehandle validation is deferred to the consuming operation and NFS4ERR_STALE returned at that point.

Gravité et risque d'exploitation

CVE-2026-89696 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 0.75 %, ce qui la place devant 54.2 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 5.15.221, <bf4d338dc8625d70c7f2cb0657d66851a7ac9154, 5.10.270, 0, 7.2.4, 6.1.188, 5.6, <=5.10.*, <=6.6.*, 6.6.157, b9e8638e3d9ed8334f1f7071e081860aac37e83e, <311f7d926630940650447cbd1c932b076b40a6c4, <00c84f4eec715e501efc080a5670114189e42507, <=6.18.*, <977e6f006a7a3ffc4216ae6034f768f8de6fd138, 7.3, <=7.2.*, <2d9846fd1c767920fddd4bde30eb35cd2969df13, <5.6, <=*, <35f248bd40b47b229d4999581df45b97daadd977, <=5.15.*, 6.18.50, 6.12.109, <ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32, <c59738a00aa51b16adc1b5ceb7c80877168efb4d) 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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