Linux Kernel: vt selection unsigned underflow & OOB read
CVE-2026-98839 Published on October 18, 2026
vt: selection: Fix unsigned underflow and slab-out-of-bounds read in paste_selection()
In the Linux kernel, the following vulnerability has been resolved:
vt: selection: Fix unsigned underflow and slab-out-of-bounds read in paste_selection()
In paste_selection(), the loop copies min_t(unsigned int,
vc_sel.buf_len - pasted,tty->receive_room) bytes per iteration into
tty_ldisc_receive_buf() and increments pasted += count.
Because the selection mutex (vc_sel.lock) is dropped inside the loop
Whenever the line discipline buffer fills up and paste_selection()
sleeps on tty->write_wait, a concurrent TIOCLINUX (TIOCL_SETSEL) ioctl
can replace vc_sel.buffer with a shorter selection and reduce
vc_sel.buf_len below pasted.
When paste_selection() resumes, vc_sel.buf_len - pasted underflows as an
unsigned integer to a large positive value, causing
tty_ldisc_receive_buf(ld, vc_sel.buffer + pasted, NULL, count) to read
up to 4094 bytes out-of-bounds past the newly allocated vc_sel.buffer.
Fix this by terminating the loop when pasted >= vc_sel.buf_len.
Kernel stack trace (Linux 7.3.0-rc3):
==================================================================
BUG: KASAN: slab-out-of-bounds in n_tty_receive_buf_common+0xa01/0x1650
Read of size 4094 at addr ffff888101c58010 by task kworker/u17:1/65
Workqueue: events_unbound flush_to_ldisc
Call Trace:
<TASK>
dump_stack_lvl+0x70/0xa0
print_report+0x153/0x4c6
kasan_report+0xf1/0x120
kasan_check_range+0x11c/0x200
__asan_memcpy+0x29/0x70
n_tty_receive_buf_common+0xa01/0x1650
tty_ldisc_receive_buf+0x66/0x110
tty_port_default_receive_buf+0x6b/0xb0
flush_to_ldisc+0x1b4/0x410
process_one_work+0x6ff/0x1110
worker_thread+0x4a8/0xb70
kthread+0x307/0x3e0
ret_from_fork+0x3ed/0x680
</TASK>
==================================================================
Products Associated with CVE-2026-98839
Want to know whenever a new CVE is published for Linux Kernel? stack.watch will email you.
Affected Versions
Linux:- Version e8c75a30a23c6ba63f4ef6895cbf41fd42f21aa2 and below 037d7e3ca5c593092f4b0d471eb869a85cbddde0 is affected.
- Version e8c75a30a23c6ba63f4ef6895cbf41fd42f21aa2 and below 619c6d7dd76fff15a9714fbf02ce299b737f01a2 is affected.
- Version e8c75a30a23c6ba63f4ef6895cbf41fd42f21aa2 and below 39495ef5d6f8019e62d65807f217a7ca8232727a is affected.
- Version 54c522782fd11a720f959ee9cb5a15bb9580343d is affected.
- Version 05c508edc9d0b44e4706d3c2cf14ee12aac210d2 is affected.
- Version e5be0e24ffc7f5783a3864b5b958088ed15be9e8 is affected.
- Version a4719f6d07b2c63223f7452c435c5f578f105cfe is affected.
- Version b4492f1e7456bd162714c0ec2815c2749d930844 is affected.
- Version 9a9c13ad21a8220cb70c9807a920f43520515f94 is affected.
- Version 8c368d36878e2fc99285279fc5e14b3d3cb8947c is affected.
- Version 3.16.83 and below 3.17 is affected.
- Version 4.4.216 and below 4.5 is affected.
- Version 4.9.216 and below 4.10 is affected.
- Version 4.14.173 and below 4.15 is affected.
- Version 4.19.109 and below 4.20 is affected.
- Version 5.4.25 and below 5.5 is affected.
- Version 5.5.9 and below 5.6 is affected.
- Version 5.6 is affected.
- Before 5.6 is unaffected.
- Version 6.18.56, <= 6.18.* is unaffected.
- Version 7.2.10, <= 7.2.* is unaffected.
- Version 7.3-rc6, <= * is unaffected.