# CVE-2025-39691

## Summary

- **CVE ID:** CVE-2025-39691
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 5, 2025
- **Last Modified:** Sep 8, 2026

## Description

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

fs/buffer: fix use-after-free when call bh_read() helper

There's issue as follows:
BUG: KASAN: stack-out-of-bounds in end_buffer_read_sync+0xe3/0x110
Read of size 8 at addr ffffc9000168f7f8 by task swapper/3/0
CPU: 3 UID: 0 PID: 0 Comm: swapper/3 Not tainted 6.16.0-862.14.0.6.x86_64
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Call Trace:
 <IRQ>
 dump_stack_lvl+0x55/0x70
 print_address_description.constprop.0+0x2c/0x390
 print_report+0xb4/0x270
 kasan_report+0xb8/0xf0
 end_buffer_read_sync+0xe3/0x110
 end_bio_bh_io_sync+0x56/0x80
 blk_update_request+0x30a/0x720
 scsi_end_request+0x51/0x2b0
 scsi_io_completion+0xe3/0x480
 ? scsi_device_unbusy+0x11e/0x160
 blk_complete_reqs+0x7b/0x90
 handle_softirqs+0xef/0x370
 irq_exit_rcu+0xa5/0xd0
 sysvec_apic_timer_interrupt+0x6e/0x90
 </IRQ>

 Above issue happens when do ntfs3 filesystem mount, issue may happens
 as follows:
           mount                            IRQ
ntfs_fill_super
  read_cache_page
    do_read_cache_folio
      filemap_read_folio
        mpage_read_folio
	 do_mpage_readpage
	  ntfs_get_block_vbo
	   bh_read
	     submit_bh
	     wait_on_buffer(bh);
	                            blk_complete_reqs
				     scsi_io_completion
				      scsi_end_request
				       blk_update_request
				        end_bio_bh_io_sync
					 end_buffer_read_sync
					  __end_buffer_read_notouch
					   unlock_buffer

            wait_on_buffer(bh);--> return will return to caller

					  put_bh
					    --> trigger stack-out-of-bounds
In the mpage_read_folio() function, the stack variable 'map_bh' is
passed to ntfs_get_block_vbo(). Once unlock_buffer() unlocks and
wait_on_buffer() returns to continue processing, the stack variable
is likely to be reclaimed. Consequently, during the end_buffer_read_sync()
process, calling put_bh() may result in stack overrun.

If the bh is not allocated on the stack, it belongs to a folio.  Freeing
a buffer head which belongs to a folio is done by drop_buffers() which
will fail to free buffers which are still locked.  So it is safe to call
put_bh() before __end_buffer_read_notouch().

## Affected Products

- Linux — Linux (1da177e4c3f41524e886b7f1b8a0c1fc7321cac2)
- Linux — Linux (2.6.12)
- Linux — Linux (0)
- Linux — Linux (5.4.297)
- Linux — Linux (5.10.241)
- Linux — Linux (5.15.190)
- Linux — Linux (6.1.149)
- Linux — Linux (6.6.103)
- Linux — Linux (6.12.44)
- Linux — Linux (6.16.4)
- Linux — Linux (6.17)

## References

- [CNA](https://git.kernel.org/stable/c/70a09115da586bf662c3bae9c0c4a1b99251fad9)
- [CNA](https://git.kernel.org/stable/c/3169edb8945c295cf89120fc6b2c35cfe3ad4c9e)
- [CNA](https://git.kernel.org/stable/c/03b40bf5d0389ca23ae6857ee25789f0e0b47ce8)
- [CNA](https://git.kernel.org/stable/c/c58c6b532b7b69537cfd9ef701c7e37cdcf79dc4)
- [CNA](https://git.kernel.org/stable/c/c5aa6ba1127307ab5dc3773eaf40d73a3423841f)
- [CNA](https://git.kernel.org/stable/c/042cf48ecf67f72c8b3846c7fac678f472712ff3)
- [CNA](https://git.kernel.org/stable/c/90b5193edb323fefbee0e4e5bc39ed89dcc37719)
- [CNA](https://git.kernel.org/stable/c/7375f22495e7cd1c5b3b5af9dcc4f6dffe34ce49)
- [CVE](https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html)
- [CVE](https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-032379.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.17%
- **EPSS Percentile:** 7.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._