CVE-2019-10639 Information

Description

The Linux kernel 4.x (starting from 4.1) and 5.x before 5.0.8 allows Information Exposure (partial kernel address disclosure) leading to a KASLR bypass. Specifically it is possible to extract the KASLR kernel image offset using the IP ID values the kernel produces for connection-less protocols (e.g. UDP and ICMP). When such traffic is sent to multiple destination IP addresses it is possible to obtain hash collisions (of indices to the counter array) and thereby obtain the hashing key (via enumeration). This key contains enough bits from a kernel address (of a static variable) so when the key is extracted (via enumeration) the offset of the kernel image is exposed. This attack can be carried out remotely by the attacker forcing the target device to send UDP or ICMP (or certain other) traffic to attacker-controlled IP addresses. Forcing a server to send UDP traffic is trivial if the server is a DNS server. ICMP traffic is trivial if the server answers ICMP Echo requests (ping). For client targets if the target visits the attacker’s web page then WebRTC or gQUIC can be used to force UDP traffic to attacker-controlled IP addresses. NOTE: this attack against KASLR became viable in 4.1 because IP ID generation was changed to have a dependency on an address associated with a network namespace.

CVSS Vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Reference

http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00014.html http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00025.html https://arxiv.org/pdf/1906.10478.pdf https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.0.8 https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=355b98553789b646ed97ad801a619ff898471b92 https://github.com/torvalds/linux/commit/355b98553789b646ed97ad801a619ff898471b92 https://lists.debian.org/debian-lts-announce/2019/07/msg00022.html https://lists.debian.org/debian-lts-announce/2019/08/msg00017.html https://seclists.org/bugtraq/2019/Aug/18 https://security.netapp.com/advisory/ntap-20190806-0001/ https://support.f5.com/csp/article/K32804955 https://support.f5.com/csp/article/K32804955?utm_source=f5support&utm_medium=RSS https://usn.ubuntu.com/4115-1/ https://usn.ubuntu.com/4118-1/ https://www.debian.org/security/2019/dsa-4497

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

NONE

Base Score

NONE

Base Severity

7.5