A vulnerability in the ext4_xattr_check_entries function of the Linux Kernel could allow a local attacker to cause a denial of service (DoS) condition on an affected system.
The vulnerability is due to improper validation of xattr sizes by the affected software when the ext4_xattr_check_entries function, as defined in the fs/ext4/super.c source code file, is used. An attacker could exploit this vulnerability by mounting a malicious ext4 image to the affected system. An exploit could trigger a NULL pointer dereference condition in the fs/posix_acl.c:get_acl() function of the affected software and cause a kernel panic, resulting in a DoS condition.
Proof-of-concept code that demonstrates an exploit of this vulnerability is publicly available.
Kernel.org has confirmed the vulnerability and released a software patch.
CVE Number – CVE-2018-1095
To exploit this vulnerability, an attacker must have local access and be a privileged user on the affected system. These requirements may reduce the likelihood of a successful exploit.
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 affected systems.
Kernel.org has released a bug report at the following link: Bug 199185
Kernel.org has released a software patch at the following link: ext4: limit xattr size to INT_MAX
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.