CVE-2026-72085

Description

In the Linux kernel, the following vulnerability has been resolved: scsi: xen: scsiback: Free unsubmitted command instead of double-putting it scsiback_get_pend_req() obtains a command tag and returns a vscsibk_pend whose embedded se_cmd has only been memset to 0, so its cmd_kref is 0; the se_cmd is initialised (kref_init() via target_init_cmd()) only later, in scsiback_cmd_exec(), on the successful VSCSIIF_ACT_SCSI_CDB path. The two error paths in scsiback_do_cmd_fn() taken before the command is submitted -- a failed scsiback_gnttab_data_map() and an unknown ring_req.act -- call transport_generic_free_cmd(&pending_req->se_cmd, 0), which kref_put()s a refcount of 0. That underflows it ("refcount_t: underflow; use-after-free") and, as the release function is not run, leaks the command tag. Impact: a pvSCSI guest can leak every command tag of a LUN's session, stopping the LUN, by submitting requests with a bad grant reference or an unknown request type; under panic_on_warn the refcount underflow panics the host. Add a helper that just returns the tag with target_free_tag() and sends the error response. It frees the tag while the v2p reference still pins the session, and snapshots the response fields beforehand because freeing the tag can let another ring reuse the pending_req slot.

Gravité et risque d'exploitation

CVE-2026-72085 obtient un score CVSS de 9.3/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.18 %, ce qui la place devant 7.1 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, 7.1.5, 6.18.40, <=6.12.*, 0, <4.6, <=7.1.*, <fa588f28401102652068c4cc75e135507f4b5106, 6.1.178, <ca978f8a93d4d36841839bf2847d29b88c2591d6, <1e97c404e44991fb087c38ccd7414f2d326f9b74, 6.12.97, <=6.6.*, <a13b789497a7fdd27d4d63f5c69d23db706ef0fe, 4.6, <=6.18.*, 5.15.212, 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, 6.6.145, <f1516c56ac540da1769f264c3cfefe4499548a5d, <=*, <fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45, <=5.15.*, <9c0f6894982b1f13bda220707497b25ac9c95bdb, 7.2) 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/9c0f6894982b1f13bda220707497b25ac9c95bdb
• https://git.kernel.org/stable/c/a13b789497a7fdd27d4d63f5c69d23db706ef0fe
• https://git.kernel.org/stable/c/fa588f28401102652068c4cc75e135507f4b5106
• https://git.kernel.org/stable/c/fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45
• https://git.kernel.org/stable/c/f1516c56ac540da1769f264c3cfefe4499548a5d
• https://git.kernel.org/stable/c/1e97c404e44991fb087c38ccd7414f2d326f9b74
• https://git.kernel.org/stable/c/ca978f8a93d4d36841839bf2847d29b88c2591d6