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CVE-2026-31707

Vulnérabilité élevée dans Linux (Linux)

CVSS 7.1 · Élevée
EPSS 0.2%
Linux•Linux•Versions : <299db777ea0cfa5c407e41b045c24a14c034c27b, 7.0.2, <d6a6aa81eac2c9bff66dc6e191179cb69a14426b, <=7.0.*, <=6.12.*, <99c631d0366c1eab8fb188fe66425f4581ebdde4, 0, 6.18.25, <7dd0c858e1909769a4c91842724315ee74f1a5f1, <=6.6.*, <5.15, <bf396208418371174869baba9434535cd3288e80, 6.6.141, 6.12.84, 7.1, 5.15, <=6.18.*, <=*, 0626e6641f6b467447c81dd7678a69c66f7746cf

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate response sizes in ipc_validate_msg() ipc_validate_msg() computes the expected message size for each response type by adding (or multiplying) attacker-controlled fields from the daemon response to a fixed struct size in unsigned int arithmetic. Three cases can overflow: KSMBD_EVENT_RPC_REQUEST: msg_sz = sizeof(struct ksmbd_rpc_command) + resp->payload_sz; KSMBD_EVENT_SHARE_CONFIG_REQUEST: msg_sz = sizeof(struct ksmbd_share_config_response) + resp->payload_sz; KSMBD_EVENT_LOGIN_REQUEST_EXT: msg_sz = sizeof(struct ksmbd_login_response_ext) + resp->ngroups * sizeof(gid_t); resp->payload_sz is __u32 and resp->ngroups is __s32. Each addition can wrap in unsigned int; the multiplication by sizeof(gid_t) mixes signed and size_t, so a negative ngroups is converted to SIZE_MAX before the multiply. A wrapped value of msg_sz that happens to equal entry->msg_sz bypasses the size check on the next line, and downstream consumers (smb2pdu.c:6742 memcpy using rpc_resp->payload_sz, kmemdup in ksmbd_alloc_user using resp_ext->ngroups) then trust the unverified length. Use check_add_overflow() on the RPC_REQUEST and SHARE_CONFIG_REQUEST paths to detect integer overflow without constraining functional payload size; userspace ksmbd-tools grows NDR responses in 4096-byte chunks for calls like NetShareEnumAll, so a hard transport cap is unworkable on the response side. For LOGIN_REQUEST_EXT, reject resp->ngroups outside the signed [0, NGROUPS_MAX] range up front and report the error from ipc_validate_msg() so it fires at the IPC boundary; with that bound the subsequent multiplication and addition stay well below UINT_MAX. The now-redundant ngroups check and pr_err in ksmbd_alloc_user() are removed. This is the response-side analogue of aab98e2dbd64 ("ksmbd: fix integer overflows on 32 bit systems"), which hardened the request side.

Gravité et risque d'exploitation

CVE-2026-31707 obtient un score CVSS de 7.1/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.17 %, ce qui la place devant 6.5 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <299db777ea0cfa5c407e41b045c24a14c034c27b, 7.0.2, <d6a6aa81eac2c9bff66dc6e191179cb69a14426b, <=7.0.*, <=6.12.*, <99c631d0366c1eab8fb188fe66425f4581ebdde4, 0, 6.18.25, <7dd0c858e1909769a4c91842724315ee74f1a5f1, <=6.6.*, <5.15, <bf396208418371174869baba9434535cd3288e80, 6.6.141, 6.12.84, 7.1, 5.15, <=6.18.*, <=*, 0626e6641f6b467447c81dd7678a69c66f7746cf) 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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