Linux Kernel inotify_update_existing_watch() Function Denial of Service Vulnerability [CVE-2019-9857]
CVE Number – CVE-2019-9857
A vulnerability in the inotify_update_existing_watch() function of the Linux Kernel could allow a local attacker to cause a denial of service (DoS) condition on a targeted system.The vulnerability exists because the inotify_update_existing_watch() function, as defined in the fs/notify/inotify/inotify_user.c source code file of the affected software, does not call fsnotify_put_mark() with IN_MASK_CREATE after fsnotify_put_mark(). An attacker could exploit the vulnerability by accessing the system and submitting malicious system calls to the affected software. A successful exploit could cause the system to crash, resulting in a DoS condition.Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available.Kernel.org has confirmed the vulnerability and released software updates.
Analysis
- To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.
Safeguards
- Administrators are advised to apply the appropriate updates.Administrators are advised to allow only trusted users to access local systems.Administrators are advised to allow only privileged users to access administration or management systems.Administrators are advised to monitor critical systems.
Vendor Announcements
- Kernel.org has released a git commit at the following link: commit 62c9d2674b31d4c8a674bee86b7edc6da2803aea
Fixed Software
- Kernel.org has released a software patch at the following link: inotify: Fix fsnotify_mark refcount leak in inotify_update_existing_watch()
Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.