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Information Exposure Affecting bpftool package, versions <0:4.18.0-193.el8

Severity

 Recommended
high

Based on CentOS security rating

    Threat Intelligence

    EPSS
    0.4% (74th percentile)

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  • Snyk ID SNYK-CENTOS8-BPFTOOL-2039721
  • published 26 Jul 2021
  • disclosed 15 Jul 2019
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Introduced: 15 Jul 2019

CVE-2019-10639 Open this link in a new tab
CWE-200 Open this link in a new tab

How to fix?

Upgrade Centos:8 bpftool to version 0:4.18.0-193.el8 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream bpftool package and not the bpftool package as distributed by Centos. See How to fix? for Centos:8 relevant fixed versions and status.

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.

References