Debian DSA-4272-1 : linux - security update

high Nessus Plugin ID 111707

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Synopsis

The remote Debian host is missing a security-related update.

Description

- CVE-2018-5391 (FragmentSmack) Juha-Matti Tilli discovered a flaw in the way the Linux kernel handled reassembly of fragmented IPv4 and IPv6 packets. A remote attacker can take advantage of this flaw to trigger time and calculation expensive fragment reassembly algorithms by sending specially crafted packets, leading to remote denial of service.

This is mitigated by reducing the default limits on memory usage for incomplete fragmented packets. The same mitigation can be achieved without the need to reboot, by setting the sysctls :

net.ipv4.ipfrag_low_thresh = 196608 net.ipv6.ip6frag_low_thresh = 196608 net.ipv4.ipfrag_high_thresh = 262144 net.ipv6.ip6frag_high_thresh = 262144

The default values may still be increased by local configuration if necessary.

Solution

Upgrade the linux packages.

For the stable distribution (stretch), this problem has been fixed in version 4.9.110-3+deb9u2.

Plugin Details

Severity: High

ID: 111707

File Name: debian_DSA-4272.nasl

Version: 1.6

Type: local

Agent: unix

Family: Debian Local Security Checks

Published: 8/15/2018

Updated: 7/15/2019

Supported Sensors: Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5.1

CVSS v2

Risk Factor: High

Base Score: 7.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS v3

Risk Factor: High

Base Score: 7.5

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

Vulnerability Information

CPE: p-cpe:/a:debian:debian_linux:linux, cpe:/o:debian:debian_linux:9.0

Required KB Items: Host/local_checks_enabled, Host/Debian/release, Host/Debian/dpkg-l

Patch Publication Date: 8/14/2018

Vulnerability Publication Date: 9/6/2018

Reference Information

CVE: CVE-2018-5391

DSA: 4272

Detections

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