Debian DSA-4272-1 : linux - security update

High Nessus Plugin ID 111707

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.

See Also

https://security-tracker.debian.org/tracker/CVE-2018-5391

https://security-tracker.debian.org/tracker/source-package/linux

https://packages.debian.org/source/stretch/linux

https://www.debian.org/security/2018/dsa-4272

Plugin Details

Severity: High

ID: 111707

File Name: debian_DSA-4272.nasl

Version: 1.6

Type: local

Agent: unix

Published: 2018/08/15

Updated: 2019/07/15

Dependencies: 12634

Risk Information

Risk Factor: High

CVSS v2.0

Base Score: 7.8

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

CVSS v3.0

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: 2018/08/14

Vulnerability Publication Date: 2018/09/06

Reference Information

CVE: CVE-2018-5391

DSA: 4272