Attacker Value
Unknown
(0 users assessed)
Exploitability
Unknown
(0 users assessed)
User Interaction
None
Privileges Required
Low
Attack Vector
Local
0

CVE-2021-4439

Disclosure Date: June 20, 2024 •
CVE-2021-4439 CVSS v3 Base Score: 7.8
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

In the Linux kernel, the following vulnerability has been resolved:

isdn: cpai: check ctr->cnr to avoid array index out of bound

The cmtp_add_connection() would add a cmtp session to a controller
and run a kernel thread to process cmtp.

__module_get(THIS_MODULE);
session->task = kthread_run(cmtp_session, session, "kcmtpd_ctr_%d",
							session->num);

During this process, the kernel thread would call detach_capi_ctr()
to detach a register controller. if the controller
was not attached yet, detach_capi_ctr() would
trigger an array-index-out-bounds bug.

[ 46.866069][ T6479] UBSAN: array-index-out-of-bounds in
drivers/isdn/capi/kcapi.c:483:21
[ 46.867196][ T6479] index -1 is out of range for type ‘capi_ctr *[32]’
[ 46.867982][ T6479] CPU: 1 PID: 6479 Comm: kcmtpd_ctr_0 Not tainted
5.15.0-rc2+ #8
[ 46.869002][ T6479] Hardware name: QEMU Standard PC (i440FX + PIIX,
1996), BIOS 1.14.0-2 04/01/2014
[ 46.870107][ T6479] Call Trace:
[ 46.870473][ T6479] dump_stack_lvl+0x57/0x7d
[ 46.870974][ T6479] ubsan_epilogue+0x5/0x40
[ 46.871458][ T6479] __ubsan_handle_out_of_bounds.cold+0x43/0x48
[ 46.872135][ T6479] detach_capi_ctr+0x64/0xc0
[ 46.872639][ T6479] cmtp_session+0x5c8/0x5d0
[ 46.873131][ T6479] ? __init_waitqueue_head+0x60/0x60
[ 46.873712][ T6479] ? cmtp_add_msgpart+0x120/0x120
[ 46.874256][ T6479] kthread+0x147/0x170
[ 46.874709][ T6479] ? set_kthread_struct+0x40/0x40
[ 46.875248][ T6479] ret_from_fork+0x1f/0x30
[ 46.875773][ T6479]

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CVSS V3 Severity and Metrics
Base Score:
7.8 High
Impact Score:
5.9
Exploitability Score:
1.8
Vector:
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector (AV):
Local
Attack Complexity (AC):
Low
Privileges Required (PR):
Low
User Interaction (UI):
None
Scope (S):
Unchanged
Confidentiality (C):
High
Integrity (I):
High
Availability (A):
High

General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
Linux e8b8de17e164
Linux not down converted
Prerequisites
Unknown
Discovered By
Unknown
PoC Author
Unknown
Metasploit Module
Unknown
Reporter
Unknown

Vendors

  • linux

Products

  • linux kernel,
  • linux kernel 5.15
Technical Analysis