In the Linux kernel, the following vulnerability has been resolved: media: rc: fix races with imon_disconnect() Syzbot reports a KASAN issue as… (CVE-2025-39993)
In the Linux kernel, the following vulnerability has been resolved: media: rc: fix races with imon_disconnect() Syzbot reports a KASAN issue as below: BUG: KASAN: use-after-free in __create_pipe include/linux/usb.h:1945 [inline] BUG: KASAN: use-after-free in send_packet+0xa2d/0xbc0 drivers/media/rc/imon.c:627 Read of size 4 at addr ffff8880256fb000 by task syz-executor314/4465 CPU: 2 PID: 4465 Comm: syz-executor314 Not tainted 6.0.0-rc1-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline] print_report.cold+0x2ba/0x6e9 mm/kasan/report.c:433 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495 __create_pipe include/linux/usb.h:1945 [inline] send_packet+0xa2d/0xbc0 drivers/media/rc/imon.c:627 vfd_write+0x2d9/0x550 drivers/media/rc/imon.c:991 vfs_write+0x2d7/0xdd0 fs/read_write.c:576 ksys_write+0x127/0x250 fs/read_write.c:631 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The iMON driver improperly releases the usb_device reference in imon_disconnect without coordinating with active users of the device. Specifically, the fields usbdev_intf0 and usbdev_intf1 are not protected by the users counter (ictx->users). During probe, imon_init_intf0 or imon_init_intf1 increments the usb_device reference count depending on the interface. However, during disconnect, usb_put_dev is called unconditionally, regardless of actual usage. As a result, if vfd_write or other operations are still in progress after disconnect, this can lead to a use-after-free of the usb_device pointer. Thread 1 vfd_write Thread 2 imon_disconnect ... if usb_put_dev(ictx->usbdev_intf0) else usb_put_dev(ictx->usbdev_intf1) ... while send_packet if pipe = usb_sndintpipe( ictx->usbdev_intf0) UAF else pipe = usb_sndctrlpipe( ictx->usbdev_intf0, 0) UAF Guard access to usbdev_intf0 and usbdev_intf1 after disconnect by checking ictx->disconnected in all writer paths. Add early return with -ENODEV in send_packet(), vfd_write(), lcd_write() and display_open() if the device is no longer present. Set and read ictx->disconnected under ictx->lock to ensure memory synchronization. Acquire the lock in imon_disconnect() before setting the flag to synchronize with any ongoing operations. Ensure writers exit early and safely after disconnect before the USB core proceeds with cleanup. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
AI Analysis
Technical Summary
This advisory covers three security fixes in the Red Hat kernel-rt packages: CVE-2025-39993 addresses race conditions in the media rc subsystem related to imon_disconnect(); CVE-2025-40240 fixes a NULL pointer dereference in SCTP when chunk data buffers are missing; and CVE-2025-68285 resolves a potential use-after-free vulnerability in the libceph function have_mon_and_osd_map(). These vulnerabilities affect the Real Time Linux Kernel used in Red Hat Enterprise Linux 8 variants. The update is rated as important and requires a reboot after installation. No CVSS scores are provided in the advisory, but the severity is assessed as high based on the nature of the flaws and Red Hat's rating.
Potential Impact
Successful exploitation of these vulnerabilities could lead to system instability or crashes due to race conditions, NULL pointer dereferences, or use-after-free bugs in kernel components. This may affect system reliability and could potentially be leveraged for denial of service or other impacts depending on the environment. The advisory does not report known exploits in the wild.
Mitigation Recommendations
Red Hat has released an official security update for the kernel-rt packages addressing these vulnerabilities. Users should apply the update as described in the Red Hat advisory RHSA-2026:0443 and reboot the system to ensure the fixes take effect. No additional mitigations are specified or required beyond applying the official patch.
In the Linux kernel, the following vulnerability has been resolved: media: rc: fix races with imon_disconnect() Syzbot reports a KASAN issue as… (CVE-2025-39993)
Description
In the Linux kernel, the following vulnerability has been resolved: media: rc: fix races with imon_disconnect() Syzbot reports a KASAN issue as below: BUG: KASAN: use-after-free in __create_pipe include/linux/usb.h:1945 [inline] BUG: KASAN: use-after-free in send_packet+0xa2d/0xbc0 drivers/media/rc/imon.c:627 Read of size 4 at addr ffff8880256fb000 by task syz-executor314/4465 CPU: 2 PID: 4465 Comm: syz-executor314 Not tainted 6.0.0-rc1-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline] print_report.cold+0x2ba/0x6e9 mm/kasan/report.c:433 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495 __create_pipe include/linux/usb.h:1945 [inline] send_packet+0xa2d/0xbc0 drivers/media/rc/imon.c:627 vfd_write+0x2d9/0x550 drivers/media/rc/imon.c:991 vfs_write+0x2d7/0xdd0 fs/read_write.c:576 ksys_write+0x127/0x250 fs/read_write.c:631 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The iMON driver improperly releases the usb_device reference in imon_disconnect without coordinating with active users of the device. Specifically, the fields usbdev_intf0 and usbdev_intf1 are not protected by the users counter (ictx->users). During probe, imon_init_intf0 or imon_init_intf1 increments the usb_device reference count depending on the interface. However, during disconnect, usb_put_dev is called unconditionally, regardless of actual usage. As a result, if vfd_write or other operations are still in progress after disconnect, this can lead to a use-after-free of the usb_device pointer. Thread 1 vfd_write Thread 2 imon_disconnect ... if usb_put_dev(ictx->usbdev_intf0) else usb_put_dev(ictx->usbdev_intf1) ... while send_packet if pipe = usb_sndintpipe( ictx->usbdev_intf0) UAF else pipe = usb_sndctrlpipe( ictx->usbdev_intf0, 0) UAF Guard access to usbdev_intf0 and usbdev_intf1 after disconnect by checking ictx->disconnected in all writer paths. Add early return with -ENODEV in send_packet(), vfd_write(), lcd_write() and display_open() if the device is no longer present. Set and read ictx->disconnected under ictx->lock to ensure memory synchronization. Acquire the lock in imon_disconnect() before setting the flag to synchronize with any ongoing operations. Ensure writers exit early and safely after disconnect before the USB core proceeds with cleanup. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
CVSS v3.1
Score 7.8high
Affected software
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This advisory covers three security fixes in the Red Hat kernel-rt packages: CVE-2025-39993 addresses race conditions in the media rc subsystem related to imon_disconnect(); CVE-2025-40240 fixes a NULL pointer dereference in SCTP when chunk data buffers are missing; and CVE-2025-68285 resolves a potential use-after-free vulnerability in the libceph function have_mon_and_osd_map(). These vulnerabilities affect the Real Time Linux Kernel used in Red Hat Enterprise Linux 8 variants. The update is rated as important and requires a reboot after installation. No CVSS scores are provided in the advisory, but the severity is assessed as high based on the nature of the flaws and Red Hat's rating.
Potential Impact
Successful exploitation of these vulnerabilities could lead to system instability or crashes due to race conditions, NULL pointer dereferences, or use-after-free bugs in kernel components. This may affect system reliability and could potentially be leveraged for denial of service or other impacts depending on the environment. The advisory does not report known exploits in the wild.
Mitigation Recommendations
Red Hat has released an official security update for the kernel-rt packages addressing these vulnerabilities. Users should apply the update as described in the Red Hat advisory RHSA-2026:0443 and reboot the system to ensure the fixes take effect. No additional mitigations are specified or required beyond applying the official patch.
Technical Details
- Gcve Source
- db.gcve.eu
- Csaf Category
- csaf_security_advisory
- Csaf Version
- 2.0
- Publisher
- Red Hat Product Security
- Advisory Id
- RHSA-2026:0443
- Cve Count
- 3
- Additional Cves
- ["CVE-2025-40240","CVE-2025-68285"]
Threat ID: 6a3da1cb4853345fc18229f6
Added to database: 06/25/2026, 21:46:51 UTC
Last enriched: 06/25/2026, 22:03:44 UTC
Last updated: 09/10/2026, 19:36:50 UTC
Views: 56
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