CVE-2025-21792

Description

In the Linux kernel, the following vulnerability has been resolved: ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt If an AX25 device is bound to a socket by setting the SO_BINDTODEVICE socket option, a refcount leak will occur in ax25_release(). Commit 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()") added decrement of device refcounts in ax25_release(). In order for that to work correctly the refcounts must already be incremented when the device is bound to the socket. An AX25 device can be bound to a socket by either calling ax25_bind() or setting SO_BINDTODEVICE socket option. In both cases the refcounts should be incremented, but in fact it is done only in ax25_bind(). This bug leads to the following issue reported by Syzkaller: ================================================================ refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 1 PID: 5932 at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Modules linked in: CPU: 1 UID: 0 PID: 5932 Comm: syz-executor424 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Call Trace: <TASK> __refcount_dec include/linux/refcount.h:336 [inline] refcount_dec include/linux/refcount.h:351 [inline] ref_tracker_free+0x710/0x820 lib/ref_tracker.c:236 netdev_tracker_free include/linux/netdevice.h:4156 [inline] netdev_put include/linux/netdevice.h:4173 [inline] netdev_put include/linux/netdevice.h:4169 [inline] ax25_release+0x33f/0xa10 net/ax25/af_ax25.c:1069 __sock_release+0xb0/0x270 net/socket.c:640 sock_close+0x1c/0x30 net/socket.c:1408 ... do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... </TASK> ================================================================ Fix the implementation of ax25_setsockopt() by adding increment of refcounts for the new device bound, and decrement of refcounts for the old unbound device.

Gravité et risque d'exploitation

CVE-2025-21792 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 0.24 %, ce qui la place devant 14.2 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions 9e1e088a57c23251f1cfe9601bbd90ade2ea73b9, 5.10.112, <5.11, <=6.1.*, 9fd75b66b8f68498454d685dc4ba13192ae069b0, <=6.12.*, 5.18, c44a453ffe16eb08acdc6129ac4fa0192dbc0456, <bca0902e61731a75fc4860c8720168d9f1bae3b6, 0, <90056ece99966182dc0e367f3fd2afab46ada847, <5.18, 6.14, <4.20, 5.15.35, <=6.6.*, 6.1.129, b20a5ab0f5fb175750c6bafd4cf12daccf00c738, 452ae92b99062d2f6a34324eaf705a3b7eac9f8b, 6.12.16, <470bda72fda0fcf54300466d70ce2de62f7835d2, 4.14.277, <94a0de224ed52eb2ecd4f4cb1b937b674c9fb955, 4.19.240, <5.5, <5.16, 5.4.190, 6.13.4, 534156dd4ed768e30a43de0036f45dca7c54818f, 5.17.2, de55a1338e6a48ff1e41ea8db1432496fbe2a62b, <=*, <b58f7ca86a7b8e480c06e30c5163c5d2f4e24023, <4.15, <=6.13.*, 6.6.79) 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/90056ece99966182dc0e367f3fd2afab46ada847
• https://git.kernel.org/stable/c/94a0de224ed52eb2ecd4f4cb1b937b674c9fb955
• https://git.kernel.org/stable/c/b58f7ca86a7b8e480c06e30c5163c5d2f4e24023
• https://git.kernel.org/stable/c/470bda72fda0fcf54300466d70ce2de62f7835d2
• https://git.kernel.org/stable/c/bca0902e61731a75fc4860c8720168d9f1bae3b6