{"id":"DEBIAN-CVE-2026-45866","details":"In the Linux kernel, the following vulnerability has been resolved:  serial: caif: fix use-after-free in caif_serial ldisc_close()  There is a use-after-free bug in caif_serial where handle_tx() may access ser-\u003etty after the tty has been freed.  The race condition occurs between ldisc_close() and packet transmission:      CPU 0 (close)                     CPU 1 (xmit)     -------------                     ------------     ldisc_close()       tty_kref_put(ser-\u003etty)       [tty may be freed here]                      \u003c-- race window --\u003e                                       caif_xmit()                                         handle_tx()                                           tty = ser-\u003etty  // dangling ptr                                           tty-\u003eops-\u003ewrite() // UAF!       schedule_work()         ser_release()           unregister_netdevice()  The root cause is that tty_kref_put() is called in ldisc_close() while the network device is still active and can receive packets.  Since ser and tty have a 1:1 binding relationship with consistent lifecycles (ser is allocated in ldisc_open and freed in ser_release via unregister_netdevice, and each ser binds exactly one tty), we can safely defer the tty reference release to ser_release() where the network device is unregistered.  Fix this by moving tty_kref_put() from ldisc_close() to ser_release(), after unregister_netdevice(). This ensures the tty reference is held as long as the network device exists, preventing the UAF.  Note: We save ser-\u003etty before unregister_netdevice() because ser is embedded in netdev's private data and will be freed along with netdev (needs_free_netdev = true).  How to reproduce: Add mdelay(500) at the beginning of ldisc_close() to widen the race window, then run the reproducer program [1].  Note: There is a separate deadloop issue in handle_tx() when using PORT_UNKNOWN serial ports (e.g., /dev/ttyS3 in QEMU without proper serial backend). This deadloop exists even without this patch, and is likely caused by inconsistency between uart_write_room() and uart_write() in serial core. It has been addressed in a separate patch [2].  KASAN report:  ================================================================== BUG: KASAN: slab-use-after-free in handle_tx+0x5d1/0x620 Read of size 1 at addr ffff8881131e1490 by task caif_uaf_trigge/9929  Call Trace:  \u003cTASK\u003e  dump_stack_lvl+0x10e/0x1f0  print_report+0xd0/0x630  kasan_report+0xe4/0x120  handle_tx+0x5d1/0x620  dev_hard_start_xmit+0x9d/0x6c0  __dev_queue_xmit+0x6e2/0x4410  packet_xmit+0x243/0x360  packet_sendmsg+0x26cf/0x5500  __sys_sendto+0x4a3/0x520  __x64_sys_sendto+0xe0/0x1c0  do_syscall_64+0xc9/0xf80  entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f615df2c0d7  Allocated by task 9930:  Freed by task 64:  Last potentially related work creation:  The buggy address belongs to the object at ffff8881131e1000  which belongs to the cache kmalloc-cg-2k of size 2048 The buggy address is located 1168 bytes inside of  freed 2048-byte region [ffff8881131e1000, ffff8881131e1800)  The buggy address belongs to the physical page: page_owner tracks the page as allocated page last free pid 9778 tgid 9778 stack trace:  Memory state around the buggy address:  ffff8881131e1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb  ffff8881131e1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb \u003effff8881131e1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb                          ^  ffff8881131e1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb  ffff8881131e1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== [1]: https://gist.github.com/mrpre/f683f244544f7b11e7fa87df9e6c2eeb [2]: https://lore.kernel.org/linux-serial/20260204074327.226165-1-jiayuan.chen@linux.dev/T/#u","modified":"2026-09-01T16:06:45.496848803Z","published":"2026-05-27T14:16:58.963Z","upstream":["CVE-2026-45866"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-45866"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.170-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not 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